You have a couple options. First would be to do a manual import of the code: Apps Code - Hubitat Documentation
You also could use Hubitat Package Manager app. You would also have to install HPM the same way as outlined in that link I posted above. But once that is done, you can just use the interface in HPM to do the install of the Lights On app, as well as many more apps and device drivers. And HPM can do updates and other things more automatically or easily, and notify you of updates. It really is the easier way once you do that initial "manual" importing step.
