You’re NOT a ‘bad’ gardener! You’re just a novice - and I’ve been doing this for 50+ years and I still learn something new nearly every day! :)
“Days 4-10: Feed the bales using a high-nitrogen organic liquid fertilizer – any standard vegetable and flower mix will be fine. Simply add it to your watering can as directed on the pack and pour onto the bales.”
https://sympathink.com/conditioning-fertilizing-straw-bales-for-gardening/
Look for a liquid fertilizer that has a high ‘N’ or FIRST number in the NPK rating. Bales need Nitrogen more so than a garden in the soil and a liquid will be the easiest way to apply it and get it to the plant roots.
They should give you some specific recommendations in any of those books suggested for Straw Bale Gardens.