Wikitree does not handle GEDCOMS very well.
If you have a small GEDCOM, you can try with that - but it has to be less than 100 names and none of those names can be dated any earlier than 1700.
It would actually be easier if you manually entered each and every person, starting with yourself, along with sources. This is what I did.
Entering 10 or 20 profiles a day will get you from 3 to 600 profiles done in a month.
If you do decide to upload a GEDCOM, then these are the FAQs.