Using JS package in custom widget

I am trying to create a widget with a chessboard using chessboardjs. I have tried retesting the js and css using

FilamenAsst::register()

FilamenAsst::register()

and flowed the instructions in the docs but I just get a

Failed to open stream: No such file or directory

Failed to open stream: No such file or directory

error. Sorry I know this must be simple to do. Thanks

Using JS package in custom widget - Filament