Privacy Settings in Instagram

Instagram users can use Privacy Settings to stop people that aren’t trusted contacts accessing their account. 

To change the Privacy settings on Instagram, 
Open the app
Select the ‘person’ icon.

This opens the User profile
Once in the ‘User Profile’, 
Select the 3-Dot menu.
Select ‘Private Account’
When an Instagram account is set to Private, only people a user accepts can access photos and videos.