Newbie question: How to remote login

Hi
Can anyone tell me what the basic steps are to do a remote login?

I’ve got an app using the acts_as_authenticated plugin, and want to add
some forum functionality.

Opinion (http://home.leetsoft.com/Opinion) says it has the ability to
remote login users but no documentation.

And I’m afraid I don’t really know where to start trying to tie this in.
If anyone could either explain hwo to do the remote loigin with things
like Opinion or just point me in the direction of a few resources for
token-based webservices, I’d be really very grateful
Thanks
Piers