There is a short document that comes with FPSCR in the docs folder that gives you the very basics of Lua scripting and how it works in FPSCR. It is not up to date with the latest information, but it does also include links to the Lua web documentation where you can learn about the language more.
Second, you can take a look at the many scripts being created by the community to see how they've made things work as well as the scripts provided in the scriptbank folder of FPSCR.
Third, look in the global.lua file for all the scripting commands available.
There are still a lot of functionality missing from scripting and there are various workarounds and known issues. So, you should definitely look through the forums here and see what is known and how to deal with various issues. A lot of us would be happy to help you further once you've taken those steps and need more assistance.
System Specs: OS - Windows 7 Home Premium 64-bit SP1, CPU - AMD Phenom II X4 945, 3.0Ghz, RAM - 8Gb DDR3, GFX Card - 2048MB NVIDIA GeForce GT 640, FPSC-R Version - Beta 1.007