How to use Workflow Elements Query - Get a Single Value

I have tried everything I know to use Aiden's tool, the "Get a Single Value" component.   Here's what I'm trying to do:

1. A payment line item record has two attributes:
   1. Cost Code lookup
   2. FIPS single text.
   3. General Ledger lookup
2. The related Cost Code record has two related "General Ledger" records
3. The General Ledger record has two attributes:
   1. ID
   2. FIPS single text

I need a workflow to run on create of the payment line item that gets me the General Ledger ID where the FIPS = the FIPS on the payment line item.

I *think* AIden's https://kaskela.wordpress.com/activity-query-for-single-value/ will do this, but I cannot figure out how to build the Query.

I really appreciate any help.