Open the "Join Discord" tab with the button in the top right of the menu. It has four sub-tabs:
Link: copy the Discord invite (click the field, Ctrl + A, Ctrl + C, paste it in your browser) and link your account: press "Link with Discord", then post the shown message (!link and a 6-digit number) in our verification channel on Discord. The code is valid for 10 min and only works in that channel – not as a direct message (DM) to the bot.
Profile: your linked Discord account, since when you are linked, your booster status and your Discord roles (reload them with "Refresh").
News: the latest announcements from our Discord as a short version, new ones are marked NEW. When a new announcement arrives you get a notice in game.
Booster: the perks for Discord boosters, the booster kit and how to boost our Discord.
First-link bonus: after linking for the first time you get the Discord role, the Discord kit (boosters also a booster kit), your rank role and a one-time 100 Radcoins (straight to your account) plus 250 scrap (in your mailbox) – only once per Steam and per Discord account. The chat is also shared between game and Discord.