Instructions
Getting the Card
Go to the Bank of Nintendo Auto Bell Dispenser (ABD), which is found in the Town Hall. It's essentially an ATM. Click "A" to use it.
Choose "Deposit."
Deposit at least 10,000 Bells. You don't need to do this all at once. The game rewards you with a Shopping Card.
Earning 10,000 Bells
Wander around the city looking for fruit trees. Each fruit tree has three fruit. Click "A" to gather them.
Go to Nook's Shop and sell the fruit. Each one is worth 100 Bells. Purchase the fishing pole for 500 Bells.
Walk to a creek, pond or lake and click "A" to throw your line. Wait until a fish yanks your bobber under water. Click "A" again to reel it in. Repeat until you've filled your inventory with fish.
Return to Nook's Shop and sell the fish. Depending on the type of fish, you might make the full 10,000 Bells in a single trip. If not, go back to the water and catch some more.