In theory, if you go to the Members page and follow the "Invite others to join" link you can invite others by email address. They will be sent a link and if they follow it then they will become a member of your site (if they already have an account it should make them a member straight away, and if they don't then they'll have to sign up for an account using the same email address that you invited them with.

If this is what you are attempting, but it isn't working, could you give me a bit more detail on what happens and I'll see if I can help further.

Thanks

Joe - Voice Admin