Ohmygod, what a cute baby you have!!
My cat was about the same age when I got him. But I didn't know enough about kittens back then and would have done things a bit differently. He should be old enough to potty on his own now. When I noticed it looked like my cat had to go, I just picked him up and put him in the litter box. I did that two times and then he was able to do it on his own. I don't know if he was a super fast learner or if that's normal. Either way, he used the litterbox every time, except once, until he passed away.
Oh and also, if you can, try and continue feeding him kitten milk (NOT cow's milk because they are lactose intolerant). I wish I had fed my kitty more milk when I first got him.
I use fancy feast and mostly stick to the dry food but we give our current cat wet food twice a week. You definitely must see the vet immediately for a check up and regularly after that. Our cat we adopted from a local shelter, we didn't go to the vet right away, and when we did bring him, they found he had ear mites which he likely got from the shelter. There are a lot of things they can find in a physical exam, such as a heart murmur and of course you want and have to get vaccines and eventually fixed.
You need a good sized, deep litter box. You don't want one that is too small because the cat won't fit into it when he's bigger. Also, check this out: https://youtu.be/LhgynG941D8 I don't use it, but it might be a good option for you!
I would recommend trying out a water fountain, if you can. Cats like running water. I have one, but unfortunately it broke, so it's just a regular water dish now but our kitty doesn't mind it.
Please be wary of the cat eating random things. My cat would always somehow find little bits of plastic to eat, even though I tried to keep things clean and throw them away. I think it's what led to him eventually having kidney disease.
Always pay attention to your cat's behavior. If he starts to do something weird, such as being lethargic, not being able to pee for a day, frequently pressing their head against a wall, or staying all day by the water dish, please don't hesitate to bring your cat to an emergency vet. I know he's young now, but make sure to have a plan about where your nearest e-vet is and also how to pay for it (Care Credit, likely). Also, consider pet insurance if you can get a deal from your work.
Okay, probably information overload at this point. XD I just learned a lot from my first kitty.