The first thing to do to change over into another plane or dimension, if one is a wizard--is to detect where the nearest other dimensions are. As stated in the Linderian introduction to dimensions space and time, planes and dimensions move and overlap just like stars, planets and galaxies.
They move in a different kind of space that has no physical form in what's called the Astral realm. Once one has crossed over into a given plane or dimension, one is existing in the material realm. Before, however and during transit one is going through non-material reality.