Go to Settings → Network & Internet → Wi‑Fi (paths may vary slightly by device/Android version).
Here’s a short, informative post about configuring proxy settings in Opera Mobile on Android. opera mobile proxy settings android
Unlike desktop browsers, Opera Mobile for Android doesn’t have a built‑in proxy configuration menu. But don’t worry—you can still route your Opera traffic through a proxy by changing the Wi‑Fi settings on your Android device. Go to Settings → Network & Internet →