There are two ways to go about performing actions in DIE Alone.
The first way is outlined in the rules and pertains primarily to rules. If something is Easy, then you must roll 1-3 on D6. Medium 4-5 of Hard is a straight 6. As your own Gamemaster, it is up to you to choose what level the Difficulty is. Reading a spellbook might be Easy for a Mage, but Hard for a Warrior, etc.
The Second is when something directly pertains to the character. In this case, you have to roll equal to, or under the Character's Stat. A character with a Smarts of 2 trying to resist a 'mind control' spell means that you must roll a 2 or below on one D6.
As I've said, I'm making a lot of this up as I go along so playtesting will determine which works better and under which circumstances, but I think that both will come to play a roll.