You don't need to! This is currently offered as a free service while in BETA. The links to your properties are located in Properties > , click 'View' on each of your properties to see your Book Now pages.
For your information, this is how the links are built (Please ignore this if you're not an advanced HTML user):
- df= the date from
- dt = the date to
- nop = number of people
- sc = your Rentals United (so bookings will appear as made by you in Rentals United)