Some tips here: How to add system apps (priv-app) on Fairphone 3 (FP3)? and here: Adding system (priv-)app after installation.
But if you are not familiar, better keep your hands away of it 
Some tips here: How to add system apps (priv-app) on Fairphone 3 (FP3)? and here: Adding system (priv-)app after installation.
But if you are not familiar, better keep your hands away of it