Karlie here from the Shopify Support Team! This error message sounds like you do not have user permissions to install apps for the Shopify account you're logged in as. Make sure you're signing in with your Account Owner login information and you shouldn't see this issue anymore. Or you can inquire with the account owner to see if you have correct permissions.
I hope this has answered your question. If not, or if you have any further questions please let me know. I will be happy to help!