Opening the lamp's page
The easiest way is the free WLED app - from the App Store for iPhone and iPad, or from Google Play for Android. With your phone on the same Wi-Fi as the lamp, the app finds the lamp by itself and lists it by its name; tap it to open its page. It finds every lamp you have, so all of them are in one list.
Without the app, open the lamp's name followed by .local in a browser on the same network - for example http://ice-light-7d3f.local or http://cube-7d3f.local. If your device does not find it by name, look up the lamp's address in your router's list of devices and open that instead.
The lamp's page is served over plain
http://only - there is nohttps://version of it. Some browsers switch an address tohttps://by themselves, and the page then does not load. If that happens, type the address withhttp://in front, or allow the browser to open this address without https when it asks. The WLED app is not affected.
In the browser, save the page to your home screen: it then opens like an app.