I have no way of knowing if your server is online or not. If you can access it using MCMA then I would assume so. In MCMA make sure you press Stop Server and wait for it to say server is offline. Then using your choice of FTP client, navigate to the directory that holds your server. Place your jar in there called ForgeMod.jar, close FTP, make sure MCMA is set to Forge for server type, then click start.
If for some reason you don't have FTP access then you have a poor host that doesn't support customization of your server in anyway. Also, don't ask your host for help, most helpdesk type people are trained to tell you they don't support custom jar files.