Hi JessieJ and welcome!! I suggest you read the first 10 pages or so in the beginners section. There, you will find a lot of extremely helpful information. What do you mean what to prepare for? Are you looking for supplies or warnings to be aware of?
As for supplies, you will need a stick blender, either stainless steel or plastic containers (#5 in the triangle on the bottom), stainless or silicone spoons, a good scale, gloves, eye protection, learn to use a soap calculator (soapee.com is a good one or soapcalc.net). Another thing to always do is if you find a recipe in a book or online, be sure to run it through a soap calculator. Errors happened.
It has everything you need to make a batch of soap except water, a stick blender, and a soap-safe pot. if you like this, you can order refills of the kit, or use the recipe they provide to get your own ingredients.