You import reservations from other channels or your personal calendar using iCal links. You can also use this method to link two listings on the same channel if you want to sync availability between them. Many users do this if they list a property on Airbnb twice. Once as a whole house, and also a single room. Read this article to learn how to manually add reservations to your calendar.
Click on your profile picture in the upper right-hand corner.
Scroll down to the listing you want to import reservations to.
Click the "Settings" button next to the listing.
Add the iCal link in the text box under "Import Calendars"
You can add multiple iCal links to each listing.