You want to do a composition of a rendered 3d model on a background image of the scene. To do that you need that the perspective of the 3d model matches the perspective of the 2d background image. This can be achieved by adjusting the camera perspective in SketchUp. Or – when the background image hasn’t been created yet – by adjusting the point of view from where you take the background photo.
The general way is to import the 2d image into SketchUp and use SketchUp’s photo match feature to set up the camera perspective in SketchUp (see on Youtube). You can then either directly export an image of the current view in SketchUp – with the model composed over the image – or render the model only and compose it later in post production (in an image editor like Photoshop).
In this case, the easiest way is to export the 3d model as .kmz file (using SketchUp’s File → Export) and open the model in Google Earth. The you can navigate around, choose your perspective and take a screenshot. A problem is that new cities in Google Earth don’t allow to hide individual buildings. Your model may intersect or be hidden by existing buildings.
Another way if you have saved the camera perspective as a scene in SketchUp is to export the scene’s camera into .kmz format using a plugin, open that in Google Earth and take a screenshot of that scene, then compose it with a rendering of the model.