Welcome to UO. I hope you'll find the game as immersive and challenging and fun as I have for years. When I first started it took over a year of consistent gaming to afford my first house with some room-mates, so congratulations seem in order. Good work!
Firstly, how do i go about making chests stack on top of each other in a room?
-Once you place one chest on a tile inside a house, either lock it down or better yet - secure it (say, "i wish to secure this"). To place more chests on top, simply drag and drop to the same tile, WITHOUT actually dropping them inside your first chest. And then secure those. It's a little tricky with placement, and you will likely drop several inside that first chest before getting one to stack, but continued practice will give you stacked chests. Secure (or lock down) each one. You can use a deco tool to turn/lower/raise to fit your vision. The key component, drop it on the same tile while NOT dropping it inside the previous chest. And Raising the first chest with a deco tool would seem to me to make this much easier, altho being old school I've never tried that way (old habits.)
-To place a lantern on the outside stairs of your house simply drop it on the stairs, while standing on the stairs to make it easiest (but not the tile you're standing on) and then lock it down ("i wish to lock this down"). Then you can 'raise' it with a deco tool to what looks best to you.
- To place lanterns and torches inside your house on the walls will be a little more tricky. The basics still apply... drop that torch as close to a north or west wall as you can, lock it down, raise it up with a deco tool. However, some better looking applications use other items in combination with 'just' a torch. Or use 'rarer' items that are more expensive that are 'meant' to go on a wall. Still, you can make a torch hang on a wall by dropping it as close as possible to the wall (west or north), locking down, and raising with a deco tool.
Ugh... I hope I made some sense... Good Luck.
P.S. Deco tools are sold by NPCs either real estate, carp, or tink, i forget which, in towns. They are fairly expensive, as I recall (20k-30k), but blessed and can be used without limit by account holding characters. It is possible to duplicate almost all deco tool options with in-game items (like stacking fishsteaks to gain 'height' and simply waiting for steaks to decay leaving your 'locked down' item at it's appropriate position or dragging and dropping chests/chairs perpendicularly to the axis you wish.)
grr... maybe a beer too many? hope this helps some. will double check after the hangover.