Your GEDCOM is not imported automatically into WikiTree, meaning no profiles are created simply by uploading a GEDCOM.
As Dennis states, you must process your GEDCOM profiles first by comparing them to potential matches in WikiTree. This process is called GEDCOMpare.
Once you have completed the comparison process, you will be given an ADD button for any of your GEDCOM profiles that you have determined do not match existing WikiTree profiles. At that point, you can create new profiles.
edit: You will find your GEDCOM starting page in the My WikiTree dropdown menu: GEDCOMs. Your GEDCOMpare reports are under the appropriate heading. Click the "GEDCompare Report is ready link to go to the processing page for your GEDCOM.
If you have a large GEDCOM, you may want to create a smaller GEDCOM for easier processing. You can do so by splitting your GEDCOM.