When you get the package, it'll tell you to download the Navica app and register your account before you need to be tested. You can do this immediately beforehand if you like, but no reason not to do it in advance.

On the day of your test, you'll go to emed.com, click Start Testing, and then use your Navica credentials to log in.

You can do the test on your phone or on a laptop/desktop. I find the latter easier since I don't have to hold the phone in one hand. The testing takes place through a web browser with no other apps required. The test asks a few basic questions, tests your sound/video to make sure they work, and then you'll be placed in a virtual queue. I haven't waited more than a minute to reach someone. The person then communicates with you over audio - they'll instruct you to open the box, unwrap the contents, do each step of the test, and then the browser sets a 15-minute timer and they leave. After that, someone comes back and verifies the results with you. You get an e-mail with the results within 15 minutes and a QR code gets dropped in your Navica app.