Determine which wall you would like to hang the wall vase on, then look for a stud. You can use a stud finder if you have one by holding down the buttons and sliding it along the wall until it indicates that you have located a stud. You can use a hammer to locate a stud if you don't have, or don't want to use, a stud finder. Just lightly tap the hammer along the wall, moving from one side to the other, until you hear a sound that doesn't sound hollow. A good place to start looking for a stud is next to an outlet, because wires are usually run along studs.
At the location of the stud, measure how high you want your wall vase to hang, and make a mark with a pencil. Use a level to make sure you are measuring straight up so you don't lose the stud.
Hammer a nail into the wall where you made your mark. Don't hammer the nail all the way into the wall; you need to leave it hanging out enough to hang the wall vase from it.
Fill the vase with whatever you want it to hold.
Hang the wall vase from the nail, and step back to examine how it looks. Adjust the vase until it looks straight. You probably won't be able to use a level to determine if it is straight because it most likely won't have a straight vertical or horizontal line to follow.