Here are 2 ways to add text to pic from 2 different sites.
Google and search for a picture you would like. When you find something that you want, right click and save image as..*note, remember what folder you are saving to.
You can use any image editor. I usually use photobucket or lunapic. Here is the link to photobucket's how to. This is pretty self explanatory.
If using lunapic...
Go to lunapic.com
click on browse..find your pic that you saved
Now your picture will appear here. If you need to resize or crop it, do that first, then click on add text
Here is a video tutorial on that site that shows how
When you are finished, you want to click on file, save image and save as jpg unless it is animated then use gif. Upload to your hosting site and you can post to blogs, messages boards.