Upload is just the first step in connecting people to the tree. You then have to compare and import. This is not a quick, clean or easy process and definitely not recommended until after you have played around on Wikitree a while and gotten your feet wet on how the profiles work here.
I recommend you read a message I wrote to another person about my GEDCOM import experience and then do some research before jumping into an import.
We want you to feel comfortable here and stay around for a while to collaborate. We don't want you to get frustrated by a bad GEDCOM import experience and decide to give up on us.