Inviting the Bot
To get your bot in a guild, you'll need to invite it. Head over to the OAuth2 tab, scroll down to OAuth2 URL Generator, tick on the bot scope, and copy the generated link.

Open the generated link (paste it into your browser). Select which server to add your bot to. Here MyBot is getting added to the Testing server:

Click Authorize, fill out any captcha, and you should see your bot appear in the specified server.
