Place your entity/character on the ground, just outside of the building (to make it easier to view). Then left click on it again, and select "position" in the widget menu (should already be selected by default). Use the green arrow to move it up to what you thing the second floor level is. Then use the WASD keys, or arrow keys, to move the entity over (make sure you haven't deselected it yet). Now select "properties", in the Widget Menu. From there, you can use the "pageup/pagedown" keys to fine tune it's placement on the Y Axis (up and down); and the arrow keys for placement on the X and Z Axis (forward/backward, left/right). Use the mouse scroll wheel to zoom in and out, and left mouse button to swing the view around; while placing your object...to get the best view.
This can be tricky; but will give you the best placement control in tight, or multiple level environments.
Intel Core i7-4820K CPU @ 3.70GHz, 16GB RAM, NVIDIA GeForce GTX 770