Instruction List;

- Append the node group "RR Bokeh Maker" from the downloaded file into your scene

- Create a plane and cut out a shape with the knife of use a Boolean operation

- Add the appended geometry node modifier to the plane

- Select the camera and in the camera settings change clip start to 0.001 and turn on depth of field

- Now go to the plane and alter sliders to get best results

- To edit the lens noise go into the shader editor and use the sliders to change the noise

If your facing an issue or have any questions please feel free to contact me and i can try to help you :)