Don't fill the fryer too full of oil or else when you go to put the bird in, you'll find that the oil has to go someplace, and that's over the edge of the pot. So, if you were to do a store-bought bird, then you should fill the pot with water, put the bird in while still wrapped, pour off excess water, and then pull the bird right out. The amount of left-over water in the pot will tell you how much oil you need to use. Just keep in mind that the oil will expand some, so just a little less than how much water you had.
This is CABL.com posting #178902. Tiny Link: cabl.co/mUHG