Each Wizard may choose a number of spells equal to their level plus 1 (in addition to any Signature Spells).
When you chose your army, you must also select which Lore of Magic each of your Wizards is going to use. What lores are available to each Wizard is specified in their Army Book. It could either be one the eight Winds of Magic at the end of this book (known as the Lore of Fire, Metal, Life, Beasts, Heavens, Light, Shadow and Death), or a unique lore available only to the army in question.
Before you start deployment, you need to determine which spells any Wizards in your army know from their chosen Lore of Magic.
The spells a Wizard knows are determined by their Wizard Level and consulting the Lore of Magic in question. This is done openly before you start deployment, so both you and your opponent will be aware of the spells each Wizard has chosen. If your army includes more than one Wizard, you can choose the order in which you choose their spells.
Regardless of the Lore of Magic your Wizard has chosen to use, you will notice that the spells are numbered between Level 1 and Level 4, with Level 1 generally being easier to cast, and Level 4 being more powerful and more difficult to cast. Wizards may only choose spells of their own Level or lower.
Note: In older books, the spells are ranked 1-6. In this case, the Wizard may choose spells equal to their Wizard level plus 2.
Ordinarily, each spell can only be chosen once in the same army. If you have more than one Wizard using the same Lore, you must choose different spells for them. The only exceptions are:
If a model has no choice over which spell(s) it knows, either because it is fixed by the model's rules, or because it has 'bought' a specific spell as part of army selection (such as Bound Spells, described later).
If the army book or spell lore clearly states that a model can exchange another spell for the spell in question.
If all the spells from the same lore are already used by other wizards in the army. Note that in this case, you must distribute any duplicate spells out as evenly as possibly between your wizards.