The first post in
"Joining SFSE's Discord Server" explains things reasonably well. First you have to visit the invitation link. Then post a reply to the topic with your SFSE nickname, Discord nickname and number.
Besides, if you're asking for help,
Help Requests is the right place to create a thread. Guides is meant to be a place for guides, for example teaching other players how to improve at a minigame.
MV: Player joined. Sorted and archived.