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.
No one knows how or why this is, but the movement of other realms is mapable and appears to move like objects would in some extent of permanence and predictability.
Not to say that all otherly realms behave like objects, but the ones that do are named, mapped and scrolled in the Great Halls of The Ancient Linderian Library. Most of it is in ruins, but the parts and scrolls that do remain can be purchased from magic users and various other institutions.
Detecting Nearby Planes or Dimensions
A roll under one's EM, then
Warlocks are able to summon Time. It is important to note since dimesions are not space based, but consist in their software, of Time. Warlocks are thus able to summon planes and dimensions and traverse portals. Sundialers summon and manipulate space, meaning galaxies and stars.