Hello!
You can use them already it doesn´t really matter. With the Folio of Knowledge you´ll be able to autofinish some quests if you have enough and also you´ll get those points during lvling too. Exp Scrolls depends I´d say you can stack them so you´ll get extra exp during lvling or you can use them to push your lvl straight away but only if it´s available (Your Exp bar should be light blue to get some extra Exp; If it´s purple you´ll collect them and when you kill mobs or finish quests it´ll give you extra.)
Greetings and have fun Leveling!