In the Develop Module click on the arrow where is says Basic in the right-hand panel. White Balance will be at the top. You can also click "w" from the Library Module or the Develop Module and you will get the White Balance Eyedropper.
Do you mean PS or LR?
Although it is usually better to set White Balance in Lightroom, it can be set in Photoshop. Create either a Curves or Levels Adjustment Layer, click on the middle (gray) eyedropper, and then click on a neutral area in the photo. There are numerous other ways of adjusting color in Photoshop including using the Camera Raw Filter and using the White Balance Tool, or opening the photo as a Smart Object from Lightroom, and then opening Camera Raw by clicking on the Smart Object badge.