The following instructions are from Wimdu and can be found on their help forum here.
1. On Wimdu
Sign into your Wimdu account.
Scroll down the page to the 'Calendar Synchronisation ' area.
Copy the URL.
2. On Uplisting
Select the listing on Uplisting you wish to sync with the Wimdu listing above.
Select the 'Connect' button on the Wimdu row.
Paste the iCalendar link copied from Wimdu (above), shown in figure 1 below.
Click 'Next sync availabilities' button to export your unavailabilities to Wimdu (instructions below).
Figure 1. Import bookings from Wimdu using iCalendar