Very carefully use a small flat screwdriver and gently pry the connector from the base port. Do not pry from the side with the tube as you may break the barbed input connection.
After the connector is removed very carefully, using a small flat screwdriver, slide the plastic ring away from the connector. This loosens the grip of the tube on the barbed input connection.
Now you need to remove the connector from the existing tube. You can cut the tube to remove the connector.
Now that you have removed the connector slide the tube from the base.
Slide the new handle's tube through the opening in the base. Then slide the plastic ring onto the tube. One side of the ring is slightly recessed. That is the side that slide onto the connector. Carefully slide the tube onto the connector. Carefully slide the plastic ring toward the connector to grip the tube onto the barbed fitting. Now that everything is like the original, attach the connector to the base and secure with the 2 screws.