This example should work alongside the Getting Started section of the OMGD documentation. Check that out for information on how to start this up.
Afterwards, visiting http://localhost:3030 in your browser should show the built web version of the game client.
NOTE: Godot 4 web servers require an https context when deployed to the cloud. OMGD currently does not support https / ssl. For deployed versions, use the built executables in the game/dist folder, or run the game from Godot itself.