When you finish marking every suggested match as "MATCH" or "REJECT," you'll see ADD buttons next to the people who don't have a COMPARE button.
Based on my experience, when you are ready to start adding people, I suggest that you open a COMPARE screen for someone who is matched to a profile WikiTree, then ADD that person's (1) parents, (2) spouse, (3) children, and (4) siblings from that COMPARE screen rather than from the main GEDOMpare screen. Continue with another person who is matched in WikiTree (for example, one of the people you just added). By always starting from a person who is matched in WikiTree and adding their first-degree relatives (parents before siblings and spouse before children), you can be reasonably sure that the links between people will be preserved.