In the “Total Full/Half Bath” field on the search page, enter the desired number of full baths followed by a period and the desired number of half baths.
1.1 is one full bath and bath.
3.2 is three full baths and two half baths.
You can also click “Add/Remove Fields” on the search page, # Half Baths” and “Save Changes”. At that point, you can search the desired minimum and maximum number of half bathrooms.