FPC trunk is a little more complicated than Lazarus trunk. I guess FpcUpDeluxe is the easiest way to get it.
Assuming you have a svn client and you have fpc 3.2.0 installed it is quite easy.
svn co <correct url for fpc, I'm too lazy to check> path/to/fpctrunksources
cd path/to/fpctrunksources
make all
make install //installs the compiler in c:\pp if you are in Windows
fpcmkcfg -o .\fpc.cfg
You can supply e.g. OPT="-gl" to the make command, so that you have a fpctrunk with debug info (slower, but quite nice to have).
Bart