ShipRush should be running in the System Tray before
shipping: 
The steps are simple:
a) Open a QuickBooks Invoice, Purchase Order, or Sales Receipt
b) Select the customer
c) [optional] Enter line items on the form
d) Select the ShipRush shipping option from the ShipRush System Tray menu.
e) Process the shipment
f) Put the cursor into the QuickBooks form, and press Ctrl-V to paste in the tracking number.