My ex rescued quite a few stray kittens over the years, so I had to learn to nurse them.
For the first couple days it's quite confusing for them, so they'll be crying a lot. After they get used to you, they won't want you to leave them alone.
We used to have them sleep in a box next to our bed while they're still kittens, make it nice and cosy and put an old shirt of yours or your gf's in the box with them, too.
You can see if they are still wanting to suckle by testing with your little finger tip.
I used to use a special kitten milk from the pet store which was a formula you mix with boiling water (but make sure temperature is only warm before feeding).
After feeding, if he's burping/got the hiccups I would burp it like you would a child. After this you use a wet wipe and then gently rub its butt to encourage it to go to the toilet (the mother cat does this with its tongue). If it's about 30 days old, you may not have to do this. Put him in the litter tray after a meal and see if he'll go on his own.
Keep the litter tray nearby at first and, as he becomes more mobile, just move it closer and closer to where you eventually want it to be. If he starts peeing outside the tray, just quickly pop him into it, he'll soon get the idea.
As it's about a month old, you can start introducing wet kitten food over the next couple weeks to try and wean him off the bottle. Eventually he'll decide on his own he only wants the food and will decline the bottle when offered.
