It takes a bit of time to grasp the concept, but WikiTree doesn't use individual trees for each person. It is all 1 big tree...
As you work through your Gedcom report, if a person in your gedcom is a close match to someone already in the tree, you will be able to view the existing tree person and decide to match them to your Gedcom record. This will add the existing person to your view of the wiki tree (called Family tree). Each WikiTree person (profile) should have a profile manager listed. You can add a comment to the profile or send the profile manager a message with any questions you might have.
If they don't match with anyone already existing in WikiTree, you can add your Gedcom person to the Wiki Tree. They will be assigned a WikiTree profile using their birth surname and the next available number for that surname. You will then become that person's Profile Manager.
Suffice it to say is that, unlike Ancestry, you don't create your own family tree, but you add to the overall tree with your little branches..
Hope this helps!