How to show only the custom app that we created via APP Designer

I am so excited with the App Designer in the Microsoft Dynamics CRM. 

I get to manage to create an app with a custom sitemap and the roles.

However, I want to show the app based on security roles.

For example,  the default app is 'Dynamics 365 - custom' and I created one app called 'Event' and only sys admin and Events roles can see this app.

Then I assigned those users to the Event role.

The question is how to make the event's user only can see the 'Event' app when they access https://orgname.crm6.dynamics.com and not the default app 'Dynamics 365 -custom'

Thanks,

Yoan