You can learn how to enable integrations here.
Step 1 - Connecting your Favro organization to your GitLab project.
In the avatar menu under App Store you will find the GitLab Source Control integration. You will be asked to fill in the name of your GitLab project, the server adress (if you're using GitLab cloud just put https://gitlab.com) and your GitLab access token.
The GitLab access token is found in the Profile Settings of your GitLab account.
Now press connect in Favro and a webhook configuration will appear with a webook URL.
Now over to GitLab again. Under Project Settings you will find Webhooks. Enter the URL of your webhook to the URL field and enable push events and merge request events.
Step 2 - Creating rules between widget and GitLab project
Now go to the widget App Store through the hamburger menu of your widget.
Create a rule for the widget connected to your GitLab project.
Step 3 - Open merge request in GitLab connected to your card
Every card created in Favro get's a unique ID.
This ID needs to be connected to your merge request in GitLab, you can use multiple ID's if the request is connected to more then one card.
You will then see in the activity feed of your card that it has been connected to a request created in GitLab.