First make sure that you're logged in and you've got your Booking Engine open. Here's a guide to do that first if you need it: Setting Up Your Booking Engine
Once you've opened up your Profile, it should look something like this:
Go ahead and add in a description of your property in the text box that says "About Your Property". Typically, you should already have a general description that you also place on your website and you can repurpose that here as well.
Once that's done, scroll down and continue to fill in the rest of the sections such as putting in the amenities available on your property, configuring the settings of your bookings, and adding in pictures of your place.
Keep in mind that you can come back in and edit any of this information at any time!