Please follow these steps...

- Go to User Settings -> Connections -> YouTube and connect your YouTube account.
- Then check User setting -> Connections -> YouTube and you should be able to join my discord server.

- IT MIGHT TAKE SOME TIME TO YOU SEE MY DISCORD SERVER.

Article : https://support.discordapp.com/hc/en-us/articles/215162978-Youtube-Channel-Memberships-Integration-FAQ