After adding a project, you may want to enable GitLab integration to be able to comment on commits, create issues and more.
To do so, simply navigate to your Project Settings, and select the Integrations tab. It gets installed in just one click but you may need to move back and forth between Codacy and GitLab if additional permissions are required.
After installing it for a project, it needs to be enabled by a user that has project access on GitLab. For private projects, this user will by default become the GitLab user that Codacy will use to comment and create issues on GitLab.