Hi @DonnaMT,

I'll take care of this query for you.

As my colleague @Rose-A stated above, you'll need to select a client under the Drop Ship To field. Right after that, click the drop-down menu on the Ship To field and choose <Add New>.

You'll then get the popup window Add Shipping Address Information. Refer to the screenshot below:

I suggest you take a look at this article as well: Use the purchase order management worksheet. It would allow you to manage purchase orders since you mentioned you have multiple warehouses. 

Direct other questions you have in the comments below. I'll get back to you as soon as I can.