So lets start first of all you and your friend will need to download radmin vpn its free and works like a hamachi but with unlimited people and no logins.
After you download and install it you will need to create a network to your guests, after create the network create you guests users and pass and make sure to enable admin login in openbullet config
so after this copy your ipv4 in radmin and enter in url “youripv4:5000” after this you will need to login as admin or your guests will need to login with it users and pass