you're best off to make cannabutter first then substitute it for the oil needed per the box instructions. (Don't use the temp indicated on the box...275F is plenty.)

cannabudder = 50 grams powdered bud or hash:500 grams butter. Obviously you don't need that much, but there's no shame in having "extra" budder. LOL In a double boiler simmer weed in butter for 30-45 minutes, stirring often. Keep an eye on it so you don't scorch the weed, or it will taste burned. when it's done strain it thru cheesecloth into your storage container.