Access the Patch tool on the left side bar of you Photoshop and draw around the wrinkle area that you want to fix. Once done click and drag to a smooth area of the skin of similar luminosity. You will notice that the wrinkled area is smoothed out.

In order to perfect that use the Clone Stamp tool and by dragging it over the edges of the newly edited areas smooth out the uneven areas. Repeat the Patch tool application on all the wrinkled areas of your image. It is best to do this in smaller areas to achieve best blending. Once you are done again smooth out the result using the Clone Stamp tool.

Finally using the airbrushing you can smooth out the end result even more.