I have to cut out a small rectangular area from the side of this cylinder. I have created a plane and a sketch and tried to extrude cut but I cannot choose to cut into the cylinder. I created a second plane and tried to select that plane for the direction of the extrusion but that isn't a thing I guess. The second image is the drawing I am replicating for my assignment. How do I cut out the area I need to cut out?

P.S. This is my first time using Solidworks (using it in college) but I have 3 years of Autodesk experience (used it in high school). Still adjusting to Solidworks.