Regardless if your lens needs repair or not, this is what you have to do first:
Find out the camera-lens distance
Find/purchase the appropriate adaptor
Attach the camera on a tripod and remove its own lens. Holding the telephoto with both hands in front of your camera with the setting of the telephoto at infinity, try to focus a very distant object. If you have a problem to keep the lens to the correct position use a paper inner tube but do not touch the internal parts of your camera.
Rotate the focusing ring a few degrees and focus again. In the final construction it is better to set the infinite point a few degrees before the rotation limit. This will allow sharp focusing by leaving some space around the correct point.
Focus on close objects. Try to find the minimum focusing distance available. In my case the distance measured was 1.7 meters at 200mm and 1.5 at 80mm.
A T-ring is the best type of adaptor for this work. It offers two possibilities for mounting a lens, either by using the 42M threading of the internal ring or by removing the ring and fitting the tube on the main connector directly. The one shown here is the Olympus Four-Thirds T-ring for DSLRs which has a bayonette type mounting.