I have to admit that 99% of the time that I do this is to pull a prank on a friend, usually by editing something they posted on Facebook. It's fast and easy to do once you know where and how to use the tool. Much to the chagrin of my Facebook friend (and Austin rocker), Adrian Conner, I'm going to use her as an example of how to edit a picture in PowerPoint (MS Word also has similar tools.)
Step One: Grab the Picture and paste it into a blank PowerPoint slide. (I think we all know how to copy and paste)
Step Two: Resize the photo (if it is too big or small) so that it fits on the slide, and then double-click the image to bring up the "Picture tools - Format" tab on PowerPoint's menu bar.
Step Three: Click the "Remove Background" icon on the Picture Tools menu tab. This will create a 'box' around a portion of the image and PowerPoint will attempt to automatically remove the background of the image. The part that is to be removed will be displayed in a purplish color.
Step Four: Move the outline box around until it is a close to the part you want to keep as possible. In this case we're removing the boxing bear and just keeping serious looking Adrian. PowerPoint does a pretty good job here of getting most of Adrian's serious stare, while removing the boxing bear. However, despite the glare, some of Adrian's hair is not there. Also the knit-toboggan is missing from her wild-haired noggin. Not to sweat it... we can edit... it. (And this is the reason I'm a blogger and not a famous lyricist.)
Step Five: To edit the parts you want to keep or delete, there is now a "Background Removal" tab that appears on the menu bar. In this case, we have areas we want to mark to keep. When you click on the "Mark Areas to Keep" tab, your mouse will turn into a pencil and you can click parts of the picture you want to keep. My suggestion is that you click around the very edges to do this. If you click outside the area, you can hit CTRL-Z to undo your click and try again, or you can press the "Delete Mark button and remove them that way. If there are areas you want to remove, you can do the same with the "Mark Areas to Remove." Again, stay around the edges until you get where you have removed (or added) everything you want to keep.
Step Six: Once you've got all the areas you want, click the "Keep Changes" button on the menu. This will remove all of the picture that is currently in that purplish hue. If it doesn't quite look right, you can click CTRL-Z again and add/remove more areas until you get it where you want it.
Step Seven: Crop the image around what is left. I usually do this because PowerPoint will keep the image the same size as the original, and if there is a much smaller area remaining, I want to crop that out. Use the "Crop" tab on the menu and pull the outline around the part you want to keep. Then press "Crop" again to remove the rest of the image.
If this is all you want to do, you can stop here, and right click on the image and "Save as Picture." However, if you want to have some fun, then follow the next steps.
Step Eight: I like to overlay these images over something outrageous. To do that, I have to make the background of the remaining picture as transparent. This will allow me to place this image on top of another image and make it look like it is a part of the picture. To do this, click on the "Color" button on the menu, and select "Set Transparent Color."
Click anywhere on the white portion of the background of the remaining picture, and it will become transparent.
Step Nine: I usually find a Google Image or a Flickr Image (make sure it is creative commons or not copyright protected if you're going to use it outside of your own personal enjoyment, e.g., post it on a Facebook.)
Paste the picture in the same slide as the one you edited, and right click on the image and click on "Send to Back." This will put your edited photo in front of the image you now want in the background. Align your picture the way you want it by making it smaller/larger so that it begins to look like it is part of the new background. If you're like me, it make take a few tries and different backgrounds to get the effect you want.
Step Ten: You can edit the color of each of the individual images, and play around with the corrections, color, and artistic effects buttons on the Format menu. Once you have it where you like it, you'll want to merge the two images together so you'll have a single final image. You can do this by selecting both images (CTRL-A works, or you can click on each and use the CTRL button as you click), and then press the "Group" button on the menu, and select "Group" from the drop down. You can then right-click and "Save as Picture" to save your final result.
It takes me about five minutes to do all the editing. It takes longer to find a good background to use than it does to actually do the editing. I find it to be very easy, and a lot of fun. Since many of us don't have editing tools like Photoshop, this is an inexpensive way to have some fun editing pictures.