Edward, Welcome to WikiTree! The way to connect is to begin with adding your parents, then grandparents and continue going back. Somewhere along the way, you will find that one or more of your ancestors is already here - added by another descendant. So, you can then just connect to that profile and, if the profile has a manager, you can contact that person and collaborate on the line.
You can also create Tags with the surnames of some of your ancestors. When you click on those tags, you can find profiles of people who also follow that particular surname.
I hope this helps and I hope you enjoy the WikiTree site.