Once you've finishing assigning tracks to your contract, you will need to add the details of those works to the contract text itself.
You can either navigate to the contract itself via the Accounting > Licensors section, or simply "View Contracts" next to the assigned contract as below to go straight to the licensors assigned contracts:
Once there you can add the details of each work assigned to that contract via the "Track Details" tab:
This will add the details of each work associated to that contract, to the top of the contract text: