After having created a contract you can link a user to this contract.
Here's how you do this:
1. Check at the level of the customer which contact persons has the ticket roll "Contract".
2. Click in your contract on the green add button behind Ticket users.
3. The "Add sales ticket user" screen will appear where you can only choose the contact persons who have been assigned a ticket control "Contract".
4. As soon as you have chosen the right contact person, you save it and the contact appears below Ticket users.
5. You have succeeded if the color of the ticket role, at the level of the contact person, changed from red to blue.