Introducing 10wk old boy to 1yr old girl

I’ve been wanting to get my cat a friend but I’ve been too nervous. Long story short I came across a stray kitten and decided it was fate lol. But I am so stressed 😩 I don’t want my resident cat to resent me or the kitten and vise versa. And as an empath or idiot idk I just feel extra deep for animals I hate leaving the new kitty in the bathroom. I have all the things he needs and a camera I can check on him and talk to him but I just am stressed

And so I’ve been visually supervising during the day and overnights new kitty stays in the bathroom and my resident has been pretty good but gotten a little more curious and with that a little more hissy/pawing. Since my kitty comes from outside she knows to his back and I’m just worried like what’s a normal “they’re hissing and growling etc” and it’s fine vs not.

It’s only the 3rd day and I know the reviews are mixed on the visual view at all during the first certain amount of time I just did what my best friend always does with her cats and I’m stressed. #HelpPls