When playing a quick match you can select your playing partners from the recent players group (people you have played with before) or you can search for them in the USGA database.

Below you will see the screens to do this:

Next, you can enter the last name of your playing partner and wait for the results to update. If it returns several players, you can use the first name input to narrow the search. You can also ask to return only members of clubs you belong to.

Once you find your player, click the name and they will be added to the match.