These necromancer skills are used to prepare a preserved corpse, so that it may become a raised undead. Raising true undead is a complicated and difficult process, and preparation is the second phase of the process.
Before preparing a corpse, the corpse must be preserved. After preparing a corpse, soul gems must be bound to it.
Note that you should keep adding soulstones until you can't add more if you want to get the most powerful undead you can.
To give your raised undead direct orders, you can use the 'order' command. To give your raised undead general battle orders, you can use the 'control' command. 'help control' will also give you an idea of how many raised undead you can have at once.
For more information about raised undead minions, see 'help undead comparison'.