First, try to set up a Harddisk. I prefer to use a directory, but you could also use a file. (Read the manual on this part, and read the part that explain the differences about a file as a harddisk or a dir...)
If you have set up a harddisk, boot with the install30/3.1 disk and use the installer to install Os3.x. Just play around a little, it's pretty easy, if you know how to setup Linux, you should be able to figure out how the setup AmigaOS....
There are plenty of sites that offer demos of games and apps (Amiga.org or
Aminet) or the game publisher themselfes..
Good luck, and welcome to the wonders that is Amiga(.org)...
Hope we were of some help, I'm outa here for now. (again