To confirm that you have the correct admin access, can you:
1. Go to your SharePoint admin center page: https://admin.microsoft.com
To confirm this, sign in to https://admin.microsoft.com as a global or SharePoint admin. (If you see a message that you don’t have permission to access the page, you don’t have Office 365 administrator permissions in your organization). Please speak to your internal IT.
2. Go to the Admin Centers page
https://admin.microsoft.com/Adminportal/Home#/homepage
2. If you don’t have an app catalog, create one. See these Microsoft instructions.
Each O365 tenant that has a working license of the installation will require an app catalog
Once you have the correct admin access and the app catalog is created you are now ready to start the installation.