in google, search for:
hammer 3.4 (you don't want 3.5 just yet)
and download it, set it up etc.
Don't try compiling with Hammer. You should check the tutorials on compiling, you need to get Batch Compiler (another job for google).
Set it up and make sure you use the hlcsg, hlbsp, hlvis, hlrad programs instead of teh qcsg, qvis etc..
Now Export your map to .map file (in Hammer, go to File / Export To Map) and Run that file in Batch.
That was all a bit long a random but just check teh tutorials and ask again if you have problems, don't make a habit of spammign questions though :