Step Four: Learn UNIX Basics
Linux is in the UNIX family, and we need to learn the basics for that family.
Googling the words "learn UNIX basics" brings up a lot of good pages. I'll give my brief introduction and suggest you then run through them.
If you have been using any computer at all you are familiar with the concepts of "documents and folders." When we talk UNIX, we say "directory" instead of "folder" and "file" in place of "document." They mean pretty much the same thing.
UNIX is organized around the idea of a place for everything and everything in its place. Directories provide the places, and files are the things.
The really nice thing from a programmer's perspective is that many of the important files in UNIX are simple text files. They can be edited with simple tools. When you learn to navigate the UNIX file tree and edit text files within it, you will have gained a very powerful tool set. You are well on your way to serving and creating web-based programs.
So you have a scratch computer, you have Linux installed, get out there and learn some UNIX basics! It will be fun. ;-)
(If you are a Linux or UNIX newbie, really take a few days at this step too.)