What is the best way to transplant a medium sized succulant in the garden. This plant is approximately 24 inches high and 5 to 6 years old.

Make sure to prep your new planting zone wether in ground or into a new pot, keep roots shaded n out of sunlight as much as possible, use superthrive & water the plant after transplanting.

Jaime told you well, but look up some YouTube videos, there are tons on these topics.

Dig up the rootball as wide as the plant is wide and dig as deep as needed to not damage the roots. Transplant it into a container with straight cactus mix and move the plant in the shade or filtered sun to start. Also apply some vitamin b-1 or superthrive to prevent shock.