To make a field required, follow the steps below.

Go to Setup > Object Manager, and select the object where the field resides.

In this example, we'll be adding a required field to the Property object, so we'll select Property.

Select Page Layouts and choose which property record type you would like to add the required field to.

Once on the page layout, you will see all the fields associated with this property.

Hover over the field you would like to make required and click on the small wrench.

Select the Required check box in the pop up, then select OK.

You will then see the field is * required. Be sure to click Save in the top left-hand corner.

To make sure your updates have been saved, go back to the front end of Rethink and create a new property. You'll see that Address is now a required field.

Repeat these steps on any additional page layouts.