Take the short piece of tubing that you cut off in Step 1. Push one end of the tubing into the splice connector. Slide the other end of the tubing over the hose barb as far as it will go. It should fit pretty snugly. Secure the tubing to the hose barb with a piece of duct tape.
OPTIONAL, BUT RECOMMENDED Further secure the tubing to the hose barb by placing a small hose clamp over the tubing and tightening the hose clamp screw. This helps prevent the tubing from being blown off of the barb by the force of the CO2 when the squib is activated.