How do you do the glider mission on assassins creed 2

I ACII, when you reach the stage where you have to get into the Basilica San Marco (I think that's the one), Ezio will remember Leonardo Da Vinci's glider and suggest he visit him. During that stage, you will launch the glider from a high tower and crash abruptly. Another will suggest you need hot air and he will have fires lit all over town. On your second attempt, you use the fires to boost your height and make it all the way to the Basilica.

After this mission is completed, or at some stage later in the game, you can go on free flight missions over Forli from the tower just north of the docks at any time.

ShaqueNova.