Spells

To learn a spell you'll have to ask Granny or Ogg-San to teach you. To perform the spell you'll want to use "syntax cast" and remember that spells are case sensitive. Simply typing "spells" will list the ones you have in your head and typing "help Spell Name" will allow you access to the helpfile which will give you added information as well as the proper syntax. Some spells will need components ("components Spell Name" will list these) and either have them in your inventory or identify a container as a component pouch and then the items will be directly taken from the container during casting.

To find out what spells Granny (and Ogg-San) know you can simply ask Nanny Ogg about it. She is keen to tell you about it:

Nanny Ogg says: Well, Esme knows more spells than a monkey has hairs, but she
     will only teach a few of them to a wee gal like yourself.
Nanny Ogg whispers to you: She doesn't approve of people knowing too many
     spells, but sometimes she can be convinced to teach simple ones, like:
     "Mother Twinter's Yarrow Enchantment" (misc),
     "Hag's Blessing" (misc),
     "Grammer Scorbic's Household Guard" (def),
     "Mother Brynda's Call of Gravity" (off),
     "Granny Lipintense's Layer of Lard" (misc),
     "Mama Blackwing's Potent Preserver" (misc),
     "Wee Flaudia's Fluffy Ear Muffs" (dev),
     "Goodie Whemper's Apple Divination" (misc),
     "Banishing of Unnatural Urges" (def),
     "Banishing of Prying Eyes" (def),
     "Banishing of Loquacious Spirits" (misc),
     "Granny Beedle's Cooperative Credits" (misc),
     "Mama Kolydina's Instant Infestation" (def),
     "Granny Benedict's Bond of Loyalty" (misc),
     "Gammer Tumult's Amalgamator" (misc),
     "Gammer Shorga's Helpful Undergrowth" (off),
     "Nanny Revere's Traitorous Talisman" (misc),
     "Mother Harblist's Fruity Flyer" (misc),
     "Mother Feelbright's Busy Bees" (off),
     "Delusions of Grandeur" (misc) or
     "Biddy Amble's Bee Buzzer" (misc).

For more information reguaring spell sizes.