step one : copy the image link and open photopea. click file -> open more -> open from url and paste the image url.

step two : you should see this screen (picture 1) create a new layer (click or you can click layer -> new -> layer) and fill it with the colour you want the wave to be.

step three : right click on your full coloured in layer and click clipping mask! you should have something like the image below

step four : click file -> export as -> png to save it! then upload it to your site and replace the image link in the code! and boom