Hi Pat,
I think the Janome's have a similiar system to my Pfaff. The arm that is at the back of your foot stays on the machine and you only change the foot itself. Lift and push back the arm and then remove the foot and replace with the 1/4 inch foot and reengage the arm by pulling it down and forward into the back of the pressure foot. The thing I am not sure about is how the feet themselves attach on your machine, mine simply snap into place on pins on either side of the shank. Good luck and happy sewing.