Please be more specific.
You saying that you crash isn't helpful. I can't determine if you crash on game startup (in which case, I'm not here to help with that) or server joining (in which case, post the logs by going to the Log page, pressing Share, and posting the link)
Although because you have just Forge and are attempting to join a modded server, that might be your issue, as you do not have the mods that the server has installed on your client.
