How do I look up a closed wo-a by searching customer name or code?

I have at least found the search key in the lower left corner (of dba classic view) but I can't figure out where I can choose a customer name or code.  If I click on the customer name or code column, nothing happens.  I can't type the name in the search field.  Sort List doesn't have the option of sorting by customer either.  I am missing where you mean.  Please advise.

You can also speed things up considerably by archiving older closed WO but that of course depends how far back you need to refer to the older ones.