First off make sure you have the newest version of swapp link installed (the version on the play store doesn’t support this yet) you can find the newest version on swapp links g+ community HERE and HERE is a link to the current (25/2/16) apk
Now go find a watch face you like in the .facer format from facerepo or use one of several apps (android and windows) to create your own and copy it to your device (sd card/swapplink/faces/
Now open swapp link and and when the watch is full screen, swipe the face right from the left but actually grabbing the side of the face.
A new menu will appear on the left…Press and hold the clock icon for a couple of seconds and a new screen will appear when you let go…
From here you can either choose from one of the pre-installed faces or if you swipe out from the right like you did on the previous screen a new menu will appear.
Press the “other” icon and a you will go to a new screen that will have previews of the .facer faces that you have added to the sd card
Now just tap on the screen you want to use and it becomes your main watch face