Apple Business Manager - how do users download apps?

My company has grown and we are providing iphones to many employees. Many of them do not have personal Apple IDs, so we decided to use Apple Business Manager. We need employees to use a specific app, WorkMax 2, as a time clock. When setting up the new iphone, the app store does not allow the user to download app from app store. How can I fix this? We want them to be able to download apps onto their iphones.