How do I add my guild there and what badge do I need and how to get that badge?
You need Discourse Trust Level 2, aka Member to post there. Here are the requirements:
Just based on your profile, it looks like you need to do the following things:
- Visit 5 more days (not sequentially)
- Receive at least 1 more like
- Reply to at least 2 more topics
Once you do that, you’ll get Member and be able to post in Discord Communities.