The channel, usually two piece, screws into the top front of the windshield frame. Place the groove of the channel down. Start with the top upside down on the hood, the thick, rolled and stitched portion of the top fits into the groove and the top is then flipped over the passenger compartment and attached to the rollbar.
I love my bikini top, I have a hard top but haven't had it on in two years! I just run the hard doors with the bikini top year round.
Here in North Alabama it gets a little "cool" for me in the winter, but the heater does ok at low speeds, in rain you just move the seat up a bit and keep moving. Summertime, I rarely have the doors on unless I am going to do some mudding or go throught thick brush, if it rains, so what!, the humidity is so bad here it dosen't make much difference!
You may find it cheaper to buy a complete new top and have a spare than pay a close to as much for just the channel alone.