There are a few ways of doing packages.
1- It could be as a gift-product package that acts as the "balance" for your customers, as explained in this video:
2- You can give the option to pre-book the number of sessions you have on the package, and then have the Shopify auto discount rules apply the discount (if any) on the cart page.
*This is a custom implementation. A Shopify developer can handle it by looking at our Dev Docs -
https://sesami.dev/docs/storefront-integration/multiple-product-forms/
If you don't have someone to take care of this for you, we can do it for you at a cost. Please contact us to discuss this in detail: help@sesami.co
For Premium plan, we can build the experience at no additional cost. :)