You're gonna be sanding on the mouthpiece again, this time only on the last 3/4" to 7/8" from the point. What you're aiming for is a gradual slope away from where the end of the reed will lay.

Use the reed as a guide when sanding the taper. If the resulting gap is too big or too small, your clarinet may be difficult or impossible to play.

When the sanded surface is nice and smooth, you can strap on the reed using the cheapest and easiest method I can think of. Rubber band.

Be careful when wrapping the rubber band around the mouthpiece/reed. If you catch the reed with the rubber band, you'll likely tear the reed bad enough that your $5.00 clarinet will immediately become a $8.00 clarinet.

With the reed strapped on and the mouthpiece correctly shaped, give it a blow. If all has turned out well, you'll hear a loud sqwak not unlike a party favor. Stick into the body and go to the next step.--->