Hi,
You need to understand what all users need to do.
If those users are going to perform some process in manufacturing module then go for premium license.
If Users are going to create Customers, Vendors, Items, Normal Sales Process and Purchase Process and some accounting thing then you can go for Essential license.
Premium license cost you 100 dollar per month whereas Essential license cost you 70 dollars.
So choose license accordingly as per your requirement.
You can buy the license directly from Microsoft or ISV
Below is the link for Purchase license.
https://dynamics.microsoft.com/en-us/business-central/pricing/
If my answer was helpful to you, please verify it so that other users know it worked. Thank you very much.