It doesn't compile and I don't know why

First up: The arduino program has a small region at the bottom where it shows error messages in red text. Unfortunately it usually scrolls past the first error message and only shows you the last part, which is not very helpful. Make the error region larger and scroll up to find the first error message.

If you see this error: #error Tools->DOSFS should be set to SDCARD (SPI) Go to the Tools menu, find DOSFS and set it to "SDCARD (SPI)" and try again.

If you see some other error, try just pasting it into google and see what it tells you. There is a good chance that if someone else had the same problem, google will find the solution for you.

If that doesn't help, go here: http://therebelarmory.com/thread/10207/proffieboard-newbie-thread and post your config file and complete error message, and someone will help you figure out what the problem is.