Before you try any method, make sure you have a warm sunny day to ensure the vinyl is flexible. If you have a heater you can also heat the water to 92 degrees or above making it much easier to work with.
The first option, and maybe the easiest, is to use a toilet plunger. You would need to get into the water and plunge the area around the wrinkle. Plunging pulls up on the wrinkle causing the liner to spread and possibly removing it.
Another option is to use a squeegie or brush. Start in the center of the pool and push the wrinkles toward the wall of the pool. Work them all the way to the top until you can adjust the liner in the track to its original position. Be careful not to rip your liner, this one takes patience patient.
For an above ground pool you'll want to drain the water level down to just a few inches remaining. Get down on your hands and knees and push the wrinkles toward the wall all around the pool. Next take the top seat railing off the top and pull the liner taught until its smooth in that section. Repeat this process all around the pool until the liner is smooth throughout the pool.
Always remember that the best option is to hire a professional to do it for you.