To confirm that you have the correct admin access, you can:
1. Go to your SharePoint admin center page: https://admin.microsoft.com
To confirm, sign in to https://admin.microsoft.com as a global or SharePoint admin. Note: 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.
You will need “Global-administrator” level permission to access or create/use an app catalog site.
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 with a working license for its installation will require an app catalog
Once you have the correct admin access and your app catalog is created, you are ready to start your installation.