Some high end vehicles allow ride height adjustment either automatically/electronically or by some manual/mechanical adjustment. After market suspension parts are available allowing adjustment in ride height.
In theory fitting longer/stiffer springs will increase the ride height, but at some point the damper travel will limit the height obtained.
If you are serious about increasing the ride, you will probably need to replace the springs and dampers to achieve what you want. If the reason for wanting to increase the height is easy access in/out of the vehicle – raising the vehicle ride height will affect the vehicle handling.