By taking out iPhone’s USB cable from the charger and plugging in iPod’s USB cable.
Instead of "Can I..." my question was "Is it OK to...". It matters as I know that the ports will fit in and when I turn on the power it will start charging, but should I do it? As I don't know whether tiny Shuffle will be able to handle so much power. I don't want to burn it.
The voltages are the same, They are designed to charge from a USB which is 5 volts. The wall charger is going to stay with that. Those charger are standard for all iPod because of this, so apple can mass produce one wall charger. Check the chargers output if you are unsure.
I would not have said "Yes" if I thought it would burn up your iPod Shuffle :)
Yes, The wall cube for your iPhone should work perfectly with your iPod shuffle.