To be clear, not all classes prepare their spells. Wizards, Clerics and Druids do, but Sorcerers and Warlocks learn and switch spells when they level up. To make sure who works how, go to the group spellbook tab. Spellcasters who prepare spells will have greyed out spell options in their list. A blue bar at the bottom of the list shows the prepared spells' limit. If the bar is full, you will need to unprepare a spell before preparing a new one. As Maximuuus said, spells are prepared and unprepared by clicking on their icon in the spellbook at any time outside of combat.
By the way, the tutorial looks great but lacks some key explanations. Also, the immediate danger presented in the setting makes experimenting an intimidating proposition.
Last edited by Flooter; 28/03/22 01:03 PM. Reason: Clarification