1. Click on the Inventory module on the left side menu.
2. Click on Rentals.
3. Click on Add a rental.
4. In the new box that pops up, choose between an existing category or create a new one.
5. Give your new rental a title.
6. Choose how many items you have in stock, and the default duration of the rental item.
7. Choose your pricing details and tax rate, if applicable.
8. Save your changes.
You will be directed to the rental page, in which you can set up all of this item's details by navigating through the left side menu: