Make sure to take off any protective strips on the encoder before installing. Some come with protection some don't. Wear gloves to avoid getting finger grease on the strip and just be careful not to scratch it up. Be extra careful of the metal edges on the machine as they are sharp and can cut the strip or damage it. Put the right side in first and then move to the left. It's much easier to lose the spring when starting from he left so I start from the right. Make sure the strip is in the middle of the sensor but not touching. Overall it's pretty straight forward. Just avoid damaging the strip and losing the spring. I usually move the head back and forth slowly after just to be sure everything is in the right place. The encoder should not move when moving the head back and forth. If it does, it means it's not seated properly.