To learn the lua programming language visit http://lua-users.org/wiki/TutorialDirectory

To create games, press escape to switch to the editors mode.
For a list of available api functions check the official documentation webpage.

To edit system files, do "edit file.lua", if you got something messed up, run "factory_reset" to revert the changes you made.

Note that you will have to "factory_reset" whenever a new update comes, so it's better to create a folder in drive D named "Programs" and place your own programs there.