1. Create the token
In GitHub, Settings > Developer settings > Personal access tokens > Fine-grained tokens: choose the repository (or the organization's repositories) and grant Repository permissions > Issues: Read and write. Nothing else is needed. A classic token with the repo scope also works but grants far more than this integration uses.
2. Add the connection
Account settings > Integrations > Issue trackers: tracker GitHub Issues, repository as owner/repo, paste the token. Leave the base URL empty for github.com; for GitHub Enterprise Server enter https://your-host/api/v3.
3. Test, then file
Test connection reads the repository and refuses one with Issues turned off. Tickets are created with the realuptime label plus your default labels; labels that do not exist in the repository yet are created by GitHub on first use.
Go deeper
The full reference lives in the docs: API documentation. Error codes named above are each explained in the error-code reference.