How do I change my identity

I am using tin on arch, and have to say it looks good so far.

However I subscribe to groups where I would like to change my 
identity. Basically I need to set my email address as something 
other than the default.

I also can't seem to find good documentation on the internet. 
Obviosly I am not looking in the right place, but where should I 
look?

Kind regards

Benedict White