yeah so theres a few things you need to know before they can join
1. you have a dynamic dns which means you need to get a host of somekind thats free. like no-ip
the reason for this is when your modem restarts or you lose power ect ect. your dns address changes. The address you make with the host will always update to include the changed address. saves you a ton of trouble.
2. if you want other people to join you need to make sure that your ports are forwarded properly. 9-10 times people cant join because of port problems.
so to give you an example if your local address is 92.145.432.45 (find this out go to google and type whats my ip) and you lose power it will change to like 92.143.224.64 just as an example. but if you have a "host" the address they give you will never change. and it will be a address like myserver.gethere.ok
instead of numbers. you would put that name into that address box
<!-- <address>myserver.gethere.ok</address> --> like this, it may sound confusing but if you want other people over the net to connect to your server while its "private" thats what you need to do.