How do I use scrolls?

I have scrolls, but can't figure out how to use them.

When I equip them in my inventory an arrow appears, however it is not assigned to a hand and it doesn't work when I press the shout button.

My example is on PC, but it would be useful to know for all platforms.

Solution 1:

Just select it, it should show up in one of your hand (you don't actually see a scroll, but the spell animation). Just cast it then like a natural spell.

Solution 2:

I used one fighting a dragon and it does show up in your hand. When you cast it you must hold down the trigger a few seconds until the discoloration goes away.