Telegram is a pretty neat, cross-platform application that is both an instant messenger and a group chatroom tool. First, you have to download Telegram itself (Windows/Linux/OSX, but also Android and iPhone!) and then you can join our chatroom through the invite link!
Download Telegram: https://telegram.org/
Join the Moosader chatroom: https://telegram.me/joinchat/DUJ-GUGH4IdkN6snTVZOlA
(open with Telegram!)