Use different video sources, not only webcam

Desktop

Open Sources window -> select Desktop as a source -> select Full Screen

Partial desktop

Open Sources window -> select Desktop as a source -> select Partial Screen

Selected area of desktop

Open Sources window -> select Desktop as a source -> select Selected Screen Rectangle

Image file

Open Sources window -> select Image as a source -> select image file

Video file

Open Sources window -> select Video as a source -> select video file

Make screenshots manually or automatically with time interval

Open Snapshot window -> set needed parameters -> make snapshots

Make a slideshow and send it to video stream

Open Slideshow window -> add images -> start slideshow