You get an authentic result if you have a good camera and you take a photo of a screen. To get bokeh you must have a lens with long enough focal length and big aperture. With low quality camera the result can be too bad. You can also get an unwanted moire pattern because the screen and the image are both made of pixels. The task isn't so trivial as it at first seems to be.
Artificial tilted view and bokeh can be made in Photoshop. You must insert the needed spare white space or computer screen frame under your screenshot before you make other things. I handle here only a screenshot.
Distort your image to create artificial perspective:
Insert a layer mask, put there a BW gradient. Photoshop's Lens Blur needs it as blurring map. Black means no blur and white means max blur (= the set blur radius).
You must disable the layer mask to get rid of the transparency after filtering:
As you see, the edges are also blurry. It's very difficult to insert anything to the image in this phase. The possible screen frame should be in the image before blurring.
If the screen has non-matte surface, it reflects environment. You can simulate it by adding a low opacity layer which contains something in the room. The inserted reflection must be blurry also in the sharp area of the screenshot, because the reflected environment is distant.
Not asked: You can get something like this quite easily as long as you keep the resolution low: