hi, I'm not current on the 737 anymore; but I had a similar situation once.
As far as I can recall, you turn a handle in the area of the reuelling panel (seperate access door) and work with the pumps and crossfeed selector from the flightdeck to move the fuel. It is pretty slow, but it works.
Sorry, I can't provide references. Is it not in Supplementary procedures?
Otherwise a mechanic at home base should definitely be able to tell and show you.
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