Here's how you get the latest experimental code:
Grabbing the latest experimental code from Github
(if you know what Git is you can get it that way too).
Gallery needs a place to stick your photos, so do this:
mkdir var
chmod 777 var
Then point your web browser at the gallery3 directory you just downloaded. You'll see a page which looks like this.The only thing you should need to enter here is the user name and password for your MySQL database.
If you don't know what's going on at this point, try clicking continue.
After the install, you should be logged in as the admin user. Here are some things to try to get you started: