Before putting the garden hose in your pool, make sure that there are no sharp edges on the hose end that could damage your liner. Once you are certain there are no sharp edges on the hose, place it on the bottom of the hopper (the deep end of your pool) and turn the water on. As your pool fills with water you may need to smooth out any wrinkles in the liner before more than 2 inches of water covers them. Once the wrinkles are covered with water, it will be impossible to remove them.
If you are using a fire hydrant, tanker truck, or another high pressure source of water; you will need to fill the hopper of the pool with 2 inches of water from a garden hose before the high pressure source is turned on. You will need to make sure you direct the water from the high pressure source into the partially filled hopper. If the high pressure water is allowed to hit the hopper sides or bottom directly, it can cause impressions in the freshly troweled vermiculite under the liner and disturb the otherwise smooth pool bottom.