First you must compile the .map into a .bsp, then you need to pack the .bsp into a .pk3
Use winzip or another zip utility to do this. Inside the .zip file put the .bsp inside a directory called maps.
Then change the extension from .zip to .pk3 and move the file to tremulous/base
If you want to /devmap your map without packing it then put the .bsp into tremulous/maps then do a /set sv_pure 0 before /devmap.
Try the tremmapping wiki for links to various tutorials (that cover compilation and making the .pk3) and other useful resources:
http://tremmapping.pbwiki.com/