at top of the cylinder just you need define dimension and then define the hole size
To crate the hole to be concentric first select the surface in which hole to be placed and use the reference as the outer circle, now using the concentric circle in sketch tool u can crate as per the requirement and remove the material
the other way is to have r rectangular sketch at an offsetted distance from the axis of revolution
Just drag the green pointers on Front & Right plane.
Watch this video.