Yunohost has an administrator web interface. The other way to administer your Yunohost install is through the CLI called "moulinette"
Please note that the web interface is an active work-in-progress and has far fewer features than the CLI moulinette.
You can access your administrator web interface at this address: https://your-domain.org/ynhadmin (replace 'your-domain.org' with your own domain name)