The controls on the Agfa isolette 1 are very simple. On the body you have two buttons and a dial. The smaller button is for releasing the fold down front cover - it is always best to lower these covers down gently and not let them pop open under the full force of the spring. The other button is the shutter release and the dial (on the far right in the picture above) is for winding the film on.
On the lens assembly, you have the shutter cock and the aperture slider and the front element rotates for focussing. There is also a screw thread which takes a standard shutter release cable and a flash connection socket. The shutter speed itself is set with the large knurled ring. Make sure that the arrow is lined up with one of the shutter speeds - in between speeds can be set but the shutter will not work correctly.
So to take a picture with the Agfa Isolette 1 you cock the shutter, set the focus distance, set the aperture, set the shutter speed, look through the viewfinder and compose your shot and then press the shutter release button. Easy! Then, remember to wind on the film ready for the next shot. This is important with this camera! There is no double exposure prevention mechanism. It is best to sort out a procedure and stick to it, so with all my folders, I wind on the film AFTER a shot, ready for the next shot. Since you have to manually cock the shutter this is relatively safe to do.