Step 1 : turn the Cricut over and remove the 4 rubber feet on the bottom
Step 2 : Now unscrew the 4 screws that are located under the rubber feet
Step 3: Position the stacker, paying attention to the "front" marking, this must be at the front.
Step 4: Attach the stacker with the included screws
Complete!
The process is the same for the upper and lower Cricut. If you're installing 2 Cricut, it's best to start with the top one.
I would always recommend keeping the original parts.