Aquatank has two openings: one for filling and the other located near the label for draining.
To fill, simply unscrew the cap on the fill opening and fill the tank with a garden hose*, through the sleeve. The (red) faucet should be in the off position and screwed on tightly to the drain opening at the opposite end of the bag near the Aquatank label. Once it is filled with water, replace the cap on the fill sleeve. When the tank is almost full, push against the back of the unit to raise the fill sleeve up higher. This will help you get the maximum number of gallons into your unit. Two people may be required. Or, place the unit on a slight angle making the faucet slightly lower than the fill side.
*Walmart has a Better Homes and Garden brand garden hose that is made with food grade material.
Place your Aquatank on a clean level surface which is well supported. It would be prudent to place a tarp under Aquatank before filling. Therefore, the smaller sizes can be moved by dragging the tarp. Do not leave the tank unattended while filling.
Other Considerations:
Store your unused Aquatank in a safe, cool, dry and clean place. If you are reusing Aquatank, repurify it by swishing it with a mixture of 2 gallons of water and 8 drops of bleach (unscented - and not pool chlorine) and then fully drain. Now you can refill Aquatank. The purity of the water in Aquatank is only as good as what you put in it. Contaminated water or suspect water that is not potable should be discarded and not used for cooking or drinking.
PLEASE NOTE: Wrinkles and creases in the material will not affect performance.