You just need to upload a ZIP file with an index.html and the other files generated (you pick the name when exporting to HTML in Godot)
So export with that name and zip the files. In our case these were:
- index.wasm
- index.png
- index.pck
- index.js
- index.html
- index.audio.worklet.js
- favicon.png
Note that the ZIP file can have any name.