Editing gaphics with text

I have been clueless about this for a long time. This single issue has stopped me from creating my own website.

I have a lot of templates, microsoft frontpage, and a freeware graphics program Irfanview. Most of the templates has some type of graphic file (usally gif format) that has text in it such as “johnson"s templates” or whatever. How do I erase this and include my text instead? I also want to edit the text on the buttons that web vistors click on to navigate the site.

Thanks to that post.
Lonniewa