Hi . Download zipped clockskin file to your desktop on your Pc . Unzip the zipped clockskin file . Connect your watch to Pc with provided cable and open up file directory . Look for the clockskin folder and open it . Drag from your desktop the unzipped clockskin folded into this opened folder . Disconnect watch and re-boot . Your new clockskin will be in the list when you browse clockskins .
There are other ways to do this but this is a good start