It is important to avoid air bubbles from forming in the lower sponge, so we suggest that you insert the syringe needle through the exit hole and fill the sponge from the bottom up.
This cartridge does not have a printhead -- only an ink reservoir.
Step 1) Put the cartridge on some paper towels in an area where you can tolerate a spill.
Step 2) Turn the exit hole upward.
Step 3) Fill a syringe bottle about 1/3rd full of ink (10 ml) for color cartridge. You will need a full syringe bottle to fill the large black cartridge.
Step 4) Inject the syringe through the exit hole. Aim it so that it fills the sponge chamber. When full, tape over the exit hole, preferably with black electrical tape.
Step 5) Look at the cartridge. Hold the cartridge so that the long side runs up and down, and the ink exit hole is to the left. The sponge filled chamber should now be in the lower left. The chamber immediately above the sponge-filled chamber is connected by a small hole in the catridge baffle. This chamber is the reservoir chamber
Step 6) Take a large paper clip. Unbend the paper clip and heat the end in a flame. Use the end to melt a hole into the cartridge. Make the hole anywhere convenient in the reservoir chamber.
Step 7) Slowly fill the reservoir chamber with ink. Be sure to chase out any air bubbles.
Step 8) When the chamber is full of ink, seal the hole you've made. Make an air-tight seal. Hot glue is best, although black electrical tape will also work. Do not use scotch tape, masking tape, or duct tape, since these tapes are not air-tight. If the seal is not air tight, the cartridge may leak.
Step 9) Remove the tape from the ink exit hole.
Step 10) Set above a paper towel or sink for 5 minutes as a drip precaution. Expect a few drips -- the ink must drip for the sponge to be full. Do not allow the ink exit hole to touch the paper towel, since the paper towel will draw out the ink.
Tape over all holes during storage to prevent leaks and evaporation.