If you have the qbox kit, it came with the baby beast ‘tank’ & 2 m2 .25Ω replacement heads.
Remove the 'tank' let it cool until it is ambient temp. Press the fire button while the tank is removed. reinstall tank, press fire button for about a second, the Ω should be displayed on the screen.
Set w to around 25w take a few vapes, gradually turn up the power until you find what you like in vape quality.
Done, enjoy.