How do you photoshop pictures?

to do what you want would take up more room than is available here anyway it takes time patience and practice to learn how to use an image editor.

the best advice I can give you is to load a picture and play with the tool available to find out what they do and how to do it if you need more information on a tool of function you can press the F1 key while you have the program open it'll open up the programs help files

Did you try Google? Gimp Tutorials gives many links, like this one

http://www.gimp.org/tutorials/