Contracts on Listings linked to a Project and Stage work in exactly the same way as they would if the Listing wasn't linked to a Project and Stage.
The only exception to the above is when the Listing has an active hold. If you click on the add contract button, instead of the usual Add contract dialog appearing, a confirmation dialog will appear and ask if you want to create a contract from the hold.
See the instructions here on creating a contract from a hold.