as i havent had time to do a full faq,I found that first you need to do is set all the enviroment viables setting LCLIMPORTDIR to point to the imports subdirectory in your splint directory,LARCH_PATH points to the lib subdirectory.You need to #include lint.h in your source file so that the compiler specific data types are recognised,and you need to point splint at the include files for your compiler with the -I flag so it looks something like
splint -I ..\include\mcs51 foo.c as it would in my case if i wanted splint to analyse foo.c
sometimes splint cannot parse #defines in which case you can use

#ifndef S_SPLINT_S

#define bad stuff

#define more bad stuff
...
..
#endif
there are about a million billion different flags you can set or unset to make splint more or less pedantic in its checks which I will outline better when ive had more time to do a complete faq.

however once installed you can type splint -help flags full
which gives you about 15 pages of descriptions of what all the flags do.
If you type splint -help vars it will show you if the enviroment variables are set.
That will have to do for now.