To fill your Mini V4 vape tank, first turn it upside down so that the mouthpiece is pointing towards the floor.
Then, unscrew the rough-textured section from the rest of the tank and put this to one side.
Take your choice of e-liquid or e-juice, and squeeze it into the sides of the tank, around the center post, being careful not to fill above the top of this post or get any liquid inside it.
Then, take the rough-textured section and screw it back into place.
Turn the tank back the right way, pop it back onto your battery, and you're good to go!
If this is your first time filling the tank, leave it to sit for around 15 minutes for use to ensure that the coil is properly saturated in e-liquid.