I have enabled a scroll, but when I click on either mouse button, nothing seems to happen. Help, please? (This must sound like a dumb request).

So you have the scroll equipped? What type of scroll is it? If it is for instance a fire storm or a scroll of blizzard, you have to hold it down for a while so that the spell charges up. Otherwise it should just fire instantly.

And some conjuration spells/scrolls have limited range. you have to point to a place not to far from you.

Maybe for some scrolls, you will also have to hold down both buttons?