Yes, I think you are right, but when you apply online you have to wait a day or two to be 'accepted' the invitations seem to include a download now button
The download link is always the same, but the backend beta messenger server will only allow people to connect that are on the list. Bear this in mind if you use multiple passport accounts on your PC, or if more than one person uses your instance, as they will each need to be onthe lsit via an invitation.
I was just invited by a friend and have downloaded, how do I go about using my invitations? I haven't had an e-mail from Microsoft or anything should I have?
Do you mean how do you give invitations out or how you use the invitation you have received? If you refer to the former then I noticed a message on the top of messenger after using it for a week, but I also have a menu option under 'help' called 'beta invitations' I had 20.
Yes I was referring to the former, I clicked help and then invitations and a page loaded - I don't have any but that may because I only got the software last night.