Place them in Surveyor. Then you can select to switch to Driver if you want to drive them. Or you can select the route, then select "Create Session", then place and drive your consist.
Either way, look for the content picker on the right side of the screen, and pick the rolling stock option, Scroll the list or partially type the names of what you are looking for to bring them up. Select a loco or car, then click on the tracks where you want it. If it shows up in the wrong direction use rotate to switch it around. For other objects click where you want them, then use rotate and move tools to place them as you want.