The Book Appointments Online by Schedulista app in the Wix App Market is a third-party app that requires its own subscription separate and above your Wix website subscription.
Your app must be upgraded to "Premium" to subscribe to Schedulista. For your convenience, Wix Billing will handle your Schedulista subscription.
Note: Multi-user subscriptions
Currently, Wix Billing only supports the single user subscription plan. For the multi-user plan, you'll need to subscribe directly through Schedulista.
When you add another user to your account, you will be prompted to switch billing systems to Schedulista. If you've already subscribed through Wix, you can learn more on switching billing systems here.
You can upgrade your Schedulista app through Wix account dashboard.
(1) Sign into your Wix account
(2) On the My Sites page of your Wix dashboard, select your site
(3) On the website dashboard, select Apps from the menu on the left
(4) Click on Manage Apps
(5) On the Manage Apps page, click the Upgrade App button for the Book Appointments Online by Schedulista app
(6) On the Upgrade App Plans page, click the Select button under Premium
(7) Enter your billing information
(8) Click Submit Purchase