Changing Virtual Background in Androd mobile phone OPPO

I am asking this question for my friendS, we were having a ZOOM meeting last night,
we were requested to use a "Mid Autumn Festival" jpeg background.
a few of my friends failed to change their Virtual background.
The problem is there is NO Virtual Background Option available on their Zoom app.
my friend is using OppO 7 .

anybody here can help ?
Thanks.