No worries. Everything is fairly new concept and everyone is learning.
Here is a step by step to import a key to O3 on mobile.
Assuming you have a fresh install of your O3 on your phone. You should see a login with existing key button.
- Open O3 desktop and go to Settings (Gear icon on the left). You will see a list of wallets you have in there
- Click a pencil icon next to a wallet label.
- Use O3 Mobile to scan an encrypted key. Enter your password.
That’s it. you should be able to access your address again on your phone.
Let me know if that helps.