Scoobert

I am trying to build a custom jar to put into multicraft but I can not seem to find a decent guide as to go about building one using a custom modpack I put together for just me and a few friends. Any help on how to build the jar or even a link to a decent guide would be most appreciated, I have been beating my head against a wall for about 5 days now trying to figure it out myself. I also must mention I am running this server through mineocity so I do not have access to multicraft's directory files, but I do know how to use ftp file transfer to move things around.