If you're not that comfortable with migrating GEDCOMs between different systems, I think it's good advice to use Wikitree X to copy across the data. Wikitree makes it deliberately quite fiddly to import information from a GEDCOM - you can't import the whole thing at once like you can on most sites.
The reason for that is that Wikitree isn't a collection of everyone's individual trees - it is a single tree, onto which we all graft our bits. If any of your ancestors are already in here, you need to link onto them not add them from your own personal tree.
The GEDCOM upload tool does help you check for people already in the tree, but you'll still have to go through and add people one by one. Wikitree X might make life a bit easier until you get the hang of the Wikitree way of doing things.