You can't.

The system for item placement was changed to use the
"nifty" new physics engine and it makes item placement MUCH harder.
There is the defaul shift+click to just toss thing out of your
inventory. Good for dropping things quickly. You can then move them
by "grabbing them iwth the z key and dragging them around with your
mouse.
Or, open your inventory and click and drag an item out of it (into the
space off to the side). This is VERY picky. You can't do it standing
close to just about anything. The interface seems to need a lot of
"room" around your character, you'll get a message if that's the case.
Once it works you'll have the item in drag mode and can move it around
as you like. However, you're still not clicking to place you're
dragging.
I can't tell you how many times I've knocked all the books off a
stacking trying to adda new book to it, or just walking by the bloody
thing. The physics engine is fun for fights but I WISH there were a
way to disable it when placing housing items.
(Yeah I'm a pack rat and a collector. In Morrowind I had a house with
an entire room dedicated to book shelves. Never once sold a book, just
built an amazing library. i can't figure out how to stack books in a
book shelf in this game without making the the other books EXPLODE out.
heh)