I did get the invite and accepted. But Discord is a little tough to understand sometimes. To Direct Message (DM) people you have to click the icon in the top left with three silhouettes in it, which will then open up your "People I've chatted with" List. Then you click "Friends" and you can view your actual friends list and click on people to talk to.

I channel hop... a LOT... but you can type @mikepm74 in a discord channel and if I am in that chat server it will alert me that I was beckoned. hahaha