Okay, on the spells it depends what class you’re playing. My apologies if this is something you already know, but bards, sorcerers and warlocks, for example, don’t need to prepare spells so should be able to cast anything you pick at level up. Wizards (like Gale) and clerics (like Shadowheart) however know more spells than they can cast in any one encounter, and need to prepare them. This can be done in the Spellbook tab of the character sheet (second tab). Gale, as a wizard, can also learn some spells from scrolls, after which they can also be prepared.
There are some bugs related to prepared spells, so if all that is old news to you and doesn’t help, perhaps if you share more details of what you’re trying and what is actually happening then someone might be able to give more useful advice.