GEDCOM files are built with a linkage protocol that is only for that file. However, If you have already added names to WikiTree and they are in that file, once you match that existing Profile to someone in your file, WikiTree will use the links internal in the GEDCOM file to begin a link process on WikiTree as you expand and import your names.
There is a caveat in this GEDCOM link process in the GDCOM file. If you bring in someone, WikiTree will recognize their parents and their children and the spouse. Anything outside of that is not recognized as a family link. Grandparents and grandchildren will not be linked if you add them out of order and you would have to manually link them to the corresponding child or parent manually..
When adding or editing names on GEDCOMpare, to get the best auto-linking on WikiTree, start with someone who is already on WikiTree and follow the family line from that person up and down the line. You can then branch out from there.
One way to know if you will have link in GEDCOMpare is that when you add someone, the Add a person page will say at the top: Adding Child or Spouse or Parent of someone on WikiTree. If it says Add an Unrelated Person, they will not be linked in WIkiTree to anyone existing on WIkiTree. You may want to close that page and add someone else who is on WIkiTree. Be aware that the name you closed the page on will have been marked as completed on the GEDCOMpare Report List and you'll need to uncheck that in the first column of their name.
If adding a list of names with no existing Profiles, the WikiTree links will start from the first name added. See, not confusing at all. LOL
So if you are adding a GEDCOM file with you listed as name in it, start with you and work out from there. The auto- links should all be in order then.
See here for more hints and help on loading your first GEDCOM file to WikiTree. https://www.wikitree.com/wiki/Space:GEDCOM_File_Usage_Primer