The Contract Approval option is available under Contract Portal Settings.
Clicking on that opens a page like the below.
To add a contract approver, click on the 'Add' button. The below page appears.
Select the type of contract and give it a title. The Order field prompts user to enter a number that will be the order in which the contract has to be approved. For instance, if order is 1, then the approver will be the first stage approver for the contract.
Choose the approver name and click ‘Save’.