Hello and welcome! I'm glad you found this board as it will really help you in treating Baxter. Everyone will probably chip in this morning with tons of tips and tricks, but I just wanted to say hello right off the bat.
Could you let us know your general location (country etc.)? There are members from all over the world here and some of the info on buying insulin, proper food and home testing supplies tends to be rather country-specific.
Also everyone will want to know: What's your name? What kind of insulin is he being prescribed (most here use Lantus, others PZI)? What are you feeding him?
The food question is really important because as you may have read on here, a low carb wet food can really bring your cat's blood sugar down. But VERY IMPORTANT you don't want to start giving insulin first and then make big diet changes because his blood sugar could drop too much. That's also why it's really important to learn to home test his blood sugar - then you will know it is safe to give insulin. Sometimes vets don't suggest this because they think it will overwhelm you, but it's a big part of treating your cat safely and we will help you learn how to do it.
I know finding out that your kitty has diabetes can be very overwhelming, never mind suddenly needing to learn how to inject insulin and test the kitty's blood sugar, but you will find all the support you need here and will be a pro at it in no time at all! I had never given anyone a needle before all this and now my dad just watches in amazement when I test my Papaya's blood sugar - he thinks I've turned into a nurse! So don't worry, you can do everything you will need to and when you're unsure just ask, there are definitely people here who can help. Best wishes for you and Baxter!