Need to change forum URL, without 404ing existing links
 

I'm almost certain there's a way to do this with htaccess, but it's not something I've dabbled in much and don't have alot of time to go researching for it all, so anyone who can point me in the right direction will be greatly appreciated.

Basically, I currently have my forums at forums.url.com but I need to change that to url.com/forums (due to wordpress bridge mod).

I'll need all direct requests to forums.url.com to be redirected to url.com/forums and if possible I'd like to know if there's a way to redirect all old links to the new one.

EG
This existing link is clicked by a user: forums.url.com/threads/6-help and is converted to url.com/forums/threads/6-help

Thanks in advance for any help given. Even if you can just link me to a webpage, I'd be greatly appreciative.