Pricelists can be assigned to a customer or an order.
Assign a Price List to a Customer
If you have created a custom price list, you can assign it to a customer's account so that it will automatically be applied to that customer for their future in store orders.
After you have created the price list you can Edit the customer account by following these instructions: https://cleansupport.zendesk.com/hc/en-us/articles/360002058792-Edit-Customer-Details
When editing their profile you will see a dropdown menu where you can select the price list.
After assigning the price list you will notice that the next time you select the customer for a new order the relevant price list will be automatically selected.
Assign a Price List to an Order
From the new order page, click on the price list box.
Select the appropriate price list in the dropdown menu.