KW88 clock faces issue

I am new at this, the KW88 is my first smart watch.  The only clock skins I am able to install are the one with the png files.  Only a few works, many display the word “Crash” when attempting to run them.  Also, the faces that do work are repeated several time in the area where you can chose them.  How can I install other watch faces format like the ones ending with .watch?  Please help me.  Thanks