The transition to raw is highly dependent on the individual cat.
Some cats take longer because they don't recognise the texture or smell, some are quicker. Age also plays a large role, younger kittens are generally easier to transition.
The simplest thing to do, is next time you are preparing any human meat meals, just slice off a small chunk and 'drop' it or put it in their food bowl. See what happens, take it slowly.
Also you don't 'need' to supplement anything in a raw diet. Supplements are just a myth prople like to hang onto, for the most part. This does not mean cats don't have dietary requirements! They do, and one important one is Taurine. Rather than explain it, here's a link
www.vcahospitals.com/main/pet-health-in ... -cats/3857 if you feed whole pray, or heart, you definitely won't need to worry if your cats get enough Taurine.
Lastly, read below. :)