Hi Claresa, welcome to the tree. I'm just going to add to what Lois Tilton has said here.
You can upload a Gedcom to the tree, but it won't really bring the tree into here, what it allows you to do is like...merge in infos that are not already in the tree, you can end up with duplications.. So first off is best if you go to the lines that you are seeking more info on, create a Gedcom file of just those lines, with no more than 5000 ppl in the Gedcom. (wktree will do no more than 5000 at a time- it will give a message of unable to create if its any larger than 5000.) Once you upload this 5000 or less, you begin by viewing starting at the newest ancestor and comparing all suggestions that the wikitree program shows you, if you find any that match, you must determine which ones match, then click the checkmark box or circle (I forget which it shows).. any way by clicking that, it will allow you to create a merge.. this means that your ancestor in your gedcom is already in the tree and you're basically attaching your ancestors to that existing person. (the ones that do connect to the person, is what I'm saying here). look for the lowest number individual that matches, that way your ancestor becomes part of that existing profile. You will have a option to "Compare" your info, sources, etc..save all the info of yours that is good sourcing (not sources of other trees... we mean primary like birth, baptism, etc records, secondary like Census, school, newspaper, death, burial, government archive records, etc..anything that maybe about the person, that was written during the time periods that they lived.. but not written by them, but someone or some entity that was around during thier life time. be sure to save any info that is already existing on the profile along with your info- all of this is done in the "compare" portion of uploading your gedcom. using the scroll bars to look at both profiles side by side, this is where you decide if they are a good match.
Now there is another issue here- Hugh de Keveloic Earl... if this is someone born prior to 1700s, then in order for you to work on profile it requires that ...
1. you have signed the Honor Code & have become a member
2. you must take the pre-1700s test before working on profiles involving time periods of pre-1700 to 1500 - https://www.wikitree.com/quiz/pre_1700
3. If this person and others you want to contribute to are before 1500 then you must meet all the qualifications of pre-1500 qualifications- https://www.wikitree.com/wiki/Help:Pre-1500_Profiles
So basically you may want to create a gedcom that stops at 1700, for the ones in your gedcom lines that you are most interested in working on 1st, bring in that gedcom, do the compares, (depending on the size gedcom this could take quite a while to complete, because as Lois said, you don't want to create duplicates, please)... you can do small gedcoms and just keep bringing in a few a time if you want. once you get the hang of it, you can bring in larger ones. is up to you. Or just manually do each new profile being sure the person doesn't already exist.
As you create profiles, you will be given suggestions for possible matches, please look at each match carefully, otherwise more duplicates will be made, and this adds to the confusions in the tree. I'm dealing with a family now where 2 wives are the same person, and the kids of the couple are split between the 2 wives, making them half siblings, I'm going to have to get the profile managers to merge the wives as one to stop the confusion that is on all of these profiles just from one set of duplicates.
Anyway, if you aren't sure what or how to do this, open a new comment with "tags" attached .. asking for help with "gedcom" & "mentor", someone who works with helping new ppl understand the tree and functions will get in touch with you. you probably have had a mentor introduce themselves on your profile in your comments at the bottom of your profile page. You can also continue to post questions on G2g about anything you aren't sure about- just add tags that give an idea of what you are needing help with.. the tags will help bring in those that have interest or expertise in these subjects or areas.
Good luck and happy hunting 
(edited typos, and added addtn'l info at end)
