You import reservations from other channels or your personal calendar using iCal links. 

1. Click on your profile picture in the upper right hand corner. 
2. Click "Settings"
3. Scroll down to the listing you want to import reservations to. 
4. Click the "Settings" button next to the listing. 
5. Add the iCal link in the text box under "Import Calendars"
6. You can add multiple iCal links to each listing.