Wizards start with 4 common spells at INT x 1%. Failed spells cost 1 magic point except fumbles might cost more. Max number of spells in memory is INT/2 (+ Spell Lore modifier). Wizards use the Knowledge (Spell Lore) skill to determine what spells they can learn (common, uncommon, rare). Wizards have spell books or grimoires and also know how to summon familiars. Spells can be cast directly from the spell book but it takes much longer. Wizards can learn new spells from scrolls, spell books or by research. Wearing armour while casting spells increases the chance of a fumble.
Any character can start with 1 known spell at INT x 1% if they want and it fits with their profession and race. These characters have a spell limit of INT/4 and do not have spell books and can’t learn new spells unless they are taught them. If they get training from a wizard (which will take a while and might cost a lot) they can become proper wizards.