You can add official accounts as friends by following the steps below.
Select from list
1. Tap the add friends icon on the top right of the friends list > the official account you wish to add from Official Account Recommendations.
2. Tap Add on the pop-up.
ID search
1. Tap the add friends icon on the top right of the friends list > ID/Phone No.
2. Enter the ID of the official account starting with @.
3. Tap Add.
Let us know if we can make it better.