Click any of the fields on the form and Field Properties section will open up on the right sidebar

You can assign a default value to the field

If it is a picklist field, you can decide which picklist values are selected to be shown in the form

You can add a placeholder text for the field

You can add a help text next to the field

You can select to display the field in single row so other fields cannot be added next to this field on the form

Or make it read only so that your users can see the field on the form cannot make any changes to it

You can also set a condition for this field's visibility on the form (You can see the details on how to set visibility condition in another how to guide)

How to Change Field Properties