Thank you for reaching out to the Community for support, oswaldo-newaddit.
I'll walk you through the steps for adding your contractor. I'd be delighted to show you how:
Go to the Time menu, then choose Time team.
Select the Add team members drop-down.
Click Add Contractor.
From the Expense page, tick Add contractor.
Fill out the required fields, then Add contractor.
Once done, the Primary admin or the contractor will only be able to track time. For more information about setting up time tracking, feel free to visit this reference: Turn on and set up time tracking in QuickBooks Online.