Granting access to application only if member of a group

Hello there,

I deployed my first WAAD integration with a custom application by using Shibboleth/SAML2 protocols

Now, if I go to my portal application and click "Logon" I am successfully redirected to Azure Logon page, then I get a SAML2 token and I am redirected back to my application that allows me to use the app. So far, so good. 

In my Directory I have 10 users, synced from my on-prem AD DS with DirSync latest version (Waad Sync). 

I noticed that any user in my directory can access this application. I was wondering if there is a way to grant access to this application only if a user is member of a specific group. 

Any hint?

Thank you in advance!