Shaing an App to the users is much more than easier before with PowerApps new UI. Previously, it was a lengthy process which required several steps. This has been streamlined into a single panel now.
As we all know that Sharing a Model-Driven app requires two steps.
1) Associate one or more security roles with the App.
2) Assign the Security role to users.
Here are the steps to be followed to share the app with users.
1) Visit https://make.powerapps.com
2) Select a model-driven app and click Share.
3) Select the app then choose a security role from the list.
4) Search for a user.
5) Select the user then select a role from the list.
6) Click Share.
Hope this helps.