I remapped my whatever key it takes to cast a scroll... so now I can't cast a scroll. How do I use a scroll?

You equip it same as a weapon or spell my friend.

As Conrad says, you just put it in one of your hands, then activate that hand (However, the scrolls seems like they have a long activation time - like you have to hold the mouse down for 3 seconds or so, then you'll see your hands do an animation which indicates the scroll spell is ready, then just let go of the mouse button/controller button/key you have assigned to that hand.

Thank you. I kind of thought that might be it after i made my post. I guess I just wasn't waiting long enough because there were 20 undead coming after me.