Go to the Add/Edit tab and select the Incoming/Incomplete listing.
On the Modify Listing screen, click on the first link (it will show the property type) in the list.
On the Status tab, click on Active. You will also need to go to the Contract tab and populate the Listing Date and Expiration Date fields (those fields are blanked out each time you save a listing as Incomplete).
Click Submit Listing.
If you have errors or have missed any required fields, correct them and then Submit Listing again.