If you want to rotate one of the objects available in the scene, you need to first select it (click on it with your mouse). When it's selected, you'll see it outlined in green and a circle containing a pair of arrows surrounding it.
Once selected, drag one of the arrows around the circle, and you will be able to assign a customized rotation to the object, as you can see in the video below. A magnet allows you to easily stop at 45° and 90°.
When you want to align an object to a specific wall, you don't need to rotate the object before moving it; TilePlanner will automatically change the alignment of the object as you approach the wall (as shown below):
Click here if you want to to learn how to disable automatic rotation when moving an object close to a wall.