Your question is not clear.
If you are asking how to fill a Carto tank:
Wet the carto with a drop of e-liquid to protect the o-rings
Slip the carto into the bottom o-ring and push up to near the top.
You can - Use a filling tool, Tapered drip tip, needle tip bottle, or syringe to easily fill the tank.
You can also tip the tank and drip liquid to fill.(a pain)
You normally cannot completely fill a tank. A small air space will remain due to the lowered carto.
Slip the carto up into place and add drip tip.
Your Carto should be primed with 30 or so drops of e-liquid BEFORE starting all this.