Problems binding spells to hotbar.

[Baler]

Left click + hold on any spell 'gem' (icon) that you have memorized onto your spellbar.
Then left click any of the open 1-8 slots on your hotkey 1 window. Then you can simply press 1-8 to cast your spell.

I believe by default you can cast spells from your spellbar with Alt + 1-8.

Another way is to make a in game macro that /cast # and Left click + hold that and left click the hotkey window slot of your choice.

To remove things from your hotkey window you can Left click + hold any of the 1-8 slots then click anywhere except a window.