If you click on an object, on the right in the Quick Properties, under Visuals, you can enter in the Z coordinate (as well as the X and Y coordinates) directly. This is usually the most accurate way to set your Z axis coordinates. But you can also shift select a group of objects (red) and then select one of them (yellow) and use your mouse wheel to scroll the selected group up and down on the Z axis.
As for connecting elevators and patients to the Z axis via floors, there's a good article on the forum covering that here: https://answers.flexsim.com/questions/21278/advanced-elevator-hc.html
Essentially your going to use a net node path to get patients and staff to walk on the right floor in 3D space. The article above explains how to get elevators set up to take patients up and down floors.