You can fill the blu ACE reservoir by unscrewing the mouthpiece, pressing down on the airflow control ring and turning counter-clockwise. Once the mouthpiece is removed, fill the reservoir with e-liquid up to the 'max' line. Screw the atomiser head back onto the lower end of the mouthpiece unit until it is tightly secured. Finish by reattaching the mouthpiece (with atomiser head) to the device. This will push the e-liquid past the 'max' line which is intended, as this helps the wick absorb the e-liquid. After 5 minutes your blu ACE is ready for use.