How to connect Qfield to PostgreSQL by online?

I created a database on PostgreSQL, connect it to QGIS through PostGIS.
Next, I package for the QGIS project and send it to my mobile. But it gets an error, my phone cannot read the database, it calls the error "PostGIS???". My postpose try to collect data by Qfield and add it online to PostGIS. Is there any document talk about this topic, step by step? I am not an IT and I am a beginner in this field.