Summarize the following:
Don't bend too hard or the tag will crack in half and spill ink everywhere. This should loosen the pin and make it pop off.

Summary:
Hold the security tag with the ink cartridge side up. Grip one of the sides of the rectangular tag with a pair of pliers. Grip the other side of the tag with a different pair of pliers. Gently bend each side of the tag down using the pliers. Keep bending until it pops open.