Let's say your client is in your store and wants to sign the contract for you in-person.
You can quickly and easily print your unsigned contract by selecting 'Print' in the top right of the Project, and click 'Unsigned Contract'

Then, once they've signed the contract, click the little drop-down arrow next to the project Status and move it manually into 'Contract Signed'

Finally, you can add a scan of the signed contract into the Files section of the project