How to "apply" a price list

How to "apply" a price list

I understand what a price list is, but I do not see how it works, in practice.

Customer ACME has price list "Price for a Small Company" with an item called "Thing." "Thing costs 1.00 in that price list, and costs 2.00 in a different price list.

I find no way to ensure that the price list assigned to ACME (Price for a Small Company) is used, referenced, or enforced.  Creating a Sales Order in CRM or Books, or creating an Invoice in Books show only the default price assigned to an item.

What am I missing?

Thank you.

Ken