If you weren't already aware, one of things that have set this and other Bethesda games apart from the mold is a simple little feature that lets you pick up and move / place items, objects, and bodies in the physical world. As such, many are the hours you could spend decorating your in-game houses with the trinkets and trophies you collect during your adventures - even with the conveniences Skyrim has to offer, such as bookshelves and weapon plaques, there's still plenty you can do on your own to customize the place to your liking.
Unfortunately, the move-drag feature has been...well, it's been pretty badly butchered compared to what it used to be, so this guide is more for helping you deal with the problems that might otherwise confound you or turn you off to the feature entirely. Self-decorating is still perfectly feasible in Skyrim, provided you learn a few tricks to make it easier.
For starters, the move / drag feature can be used by moving the cursor over an item / body and holding down the action (A) button, the button normally used to talk / pick up / loot. It sounds fishy, but it's actually programmed pretty well to know the difference between 'take' and 'move / drag.'
And for the sake of ease when writing this, familiarize yourself with the term cell, which refers to a self-contained area of the game; the interior of Breezehome is a cell, the city of Whiterun within the walls is a cell, and so forth. Any time you go through a doorway and encounter a loading screen, you are passing from one cell into another.
Why the Hell Do All My Items Keep Falling On The Floor?!
This is probably the first and most prominent issue that you'll run into when trying to decorate. For reasons unbeknownst to me, whenever you drop and item for decorating purposes, the item will usually return to the point at which you dropped it when you re-enter your house (cell) after leaving it; so if you drop items and immediately decorate with them, it will look like a damn tornado ripped through your house when you come back later.
But with 99% of the game's items, this only happens once - so, when decorating, drop all the items you want to use in a big pile, leave the cell, reload the auto-save when you step outside (this allows the game a full loading screen upon re-entering and makes sure that the cell takes stock of the items you dropped), re-enter the cell, and start decorating.
And while the move-drag feature can tell the difference between 'take' and 'move / drag' pretty well, there still will be the occasional instance where you accidentally take an item back into your inventory. Don't just try and redecorate with that item - you'll have to re-drop it and repeat the exit / re-enter again. --- Simple questions deserve long-winded answers that no one will bother to read.