Forgot to buy yeast nutrient. I've heard you can use raisins...
Do I just chop them up and dump them into the primary? or do I mash them in a small amount of water ?
i would just skip it. pitch correct amount of healthy yeast and it'll be fine. Buy the nutrient and use it next batch.
I agree with lamppa. But if you really want to put them in, chop em up and put them in a mesh bag and put it in the primary.