Using magic is hardly new in games, and new spells are generallyacquired by leveling up or unlocking them in skill trees. Baldur's Gate 3 makes magic a little more complex. You still learn spells by leveling up, as well as reading scrolls if you're a Wizard, but can't unleash them all whenever you like. If you could, spellcasters would easily become overpowered among the other classes. Instead, spells need to be prepared before you can use them. Unless you go out of your way to prepare new spells, you'll be stuck with what you currently have. Here's how you can prepare your spells in Baldur's Gate 3.
How to prepare spells
After you gain your first additional spell from whichever ones you begin with, you will need to think about preparing them. Only prepared spells can be used in combat (and out of it in some instances), and there's a limit on how many you can have prepared at a time.
Step 1: Select the new spell(s) you want to learn through leveling or reading scrolls.
Step 2: While out of combat, open your Spellbook by hitting the K key.
Step 3: Here you will see your currently prepared spells in the Prepared Spells row with the rest of your learned spells below.
Step 4: To change them, click on a prepared spell to remove it, then simply choose which spell(s) you want to add.
Note that Sorcerers are unable to change prepared spells as freely as other magic classes. They are only able to swap out their spells while leveling up, so remember to do so when you have the chance.