When the controller is in AP (access point) mode, it creates its own WiFi (the one named OS_ followed by 6 letters). In that mode it has IP address 192.168.4.1. Once it’s connected to your home WiFi, its IP is no longer 192.168.4.1, you need to click B1 on the controller to find out the IP address it’s assigned. To verify if it’s connected to your home WiFi: the LCD should show 2 lines, no blinking dot (in contrast, in AP mode, it shows 4 lines with a blinking dot).
One more thing: I assume you have Internet connection on your home WiFi. If you don’t have Internet connection, you need to use the OpenSprinkler mobile app to access the controller. The reason is that the javascript files needed to render the UI are on the cloud — if you don’t have Internet connection, use the mobile app, which has these files embedded in the app.