i can't open the files
Valentines Day Chess Piece Set/Theme

Hi, @yuna-icedcoffee! You don't have to open or unzip the file. Just download from the given link and use the "Import Profile" button from the Chess.com Custom Pieces extension. After clicking "Import Profile", select the file that you just downloaded(it will be a .cext file) and the theme will be applied on your chess.com board and pieces.
Valentine's Day Piece Set/Theme
You can download the piece set/theme from here and use the Import Profile button using the Chess.com Custom Pieces extension to set the theme. Enjoy!