1. Create the token
In the project, Settings > Access tokens: role Reporter or higher, scope api. A personal access token with api also works; a project token keeps the blast radius to one project.
2. Add the connection
Tracker GitLab Issues, project as its path (group/project) or numeric id, paste the token. Leave the base URL empty for gitlab.com; for self-hosted enter the instance origin, e.g. https://git.acme.dev (it must be publicly reachable over https).
3. Test, then file
Test connection reads the project and refuses one with Issues disabled. Tickets carry the realuptime label plus your default labels, comma-joined the way GitLab expects.
Go deeper
The full reference lives in the docs: API documentation. Error codes named above are each explained in the error-code reference.