Hi Diana,
To assign a standard Fiori app role to user, you do not need to touch Launchpad Designer.
1. Find a catalog role and group role name in SAP Fiori Apps Reference Library.
2. Assign a catalog role and a group role to user in the PFCG transaction
3. Test Fiori apps in SAP Fiori launchpad
SAP Fiori - SAP Fiori launchpad troubleshooting
Regards,
Masa / SAP Technology RIG