There is a large phillips head screw on one side of the carb. Loosen this and the whole plate and rubber gasket come off. The screen is underneath.

I use a filter on the line (red aluminum filter from Hangar 9 unscews will a very fine replacable plastic screen inside which looks like a bucket- don't know the name) from my gas can and between the tank and the carb. Have not had a problem since I started filtering. Prior to that, I had a Brison and BME both quit in flight. The screen on the Brison was about half full of something but it was enough clog that the engine would not even start.

Bruce