How can I use lower level spells in higher level spell slots?

baldur's gate 3 level 1 spell slot   Dan vit 2024 slot booking

spell slots which you can get by levelling other classes Multiclass 1 level of wizard can

Baldur's Gate III Explaining spell levels in Baldur's Gate 3 and D&D

bf-680 With a level 1 spell slot, the caster can target up to three enemies with a magic missile, or send all three of them at a single target As Idk what may be the issue, but i'm lv 3 with: SIX lv 1 Spells and TWO lv2 Spells While Gale has SIX lv 1 Spells and FOUR lv