In general, you need to serve both your page and your service worker script via HTTPS in order to use service workers. The rationale is described at Prefer Secure Origins For Powerful New Features.
There's an exception to the HTTPS requirement in place to facilitate local development: if you access your page and service worker script via http://localhost[:port], or via http://127.x.y.z[:port], then service workers should be enabled without any further actions.
In recent versions of Chrome, you can work around this requirement duriing local development via chrome://flags/#unsafely-treat-insecure-origin-as-secure .
Firefox offers similar functionality, via the devtools.serviceWorkers.testing.enabled setting in about:config page.