How to refill hp officejet 940 ink cartridge?

A simple way to refill hp 920, 940 or any other printer model ink cartridges, remove ink cartridges carefully. Find and open its hole, take an syringe and fill it with ink and insert ink through the hole into the chambers. Now take care about the quantity in the chamber. The quantity of ink is different in black as compare to the coloured. Shake well your hp ink cartridges and place it. First take a some rough prints and on any papers.