If you are looking to open images from Lightroom to Photoshop, please follow the below steps.
Once you finish editing the image in Photoshop, simply save and it will back in Lightroom as a Edited copy of the image.
Refer the related article:Adobe Photoshop Lightroom Help | Edit Lightroom photos in Photoshop or Photoshop Elements
Or if you looking to open images from your computer to Photoshop, please follow the below steps.
Let us know if that helps.
A good response by Mohit.
However, going back to basics, Lightroom and Photoshop are two separate programs requiring you to install them both, one at a time.