Get books and a doll that you can mime out changing a nappy on, rocking etc. Watch TV programmes that show babies.
For the introduction, have absolutely no expectations of how older DC should behave. Forget the cute insta videos of delighted siblings.
At that point, your eldest will have been away from you for at least half a day, potentially several days and their main focus will be wanting to be reunited with you. Not caring about the baby. If older DC rushes in excited to see you then sees your arms full with baby or told to slow down not to scare baby etc, that's not the best intro as it communicates that they're now second fiddle.
We had dc2 in carry case in corner, gave dc1 a big cuddle and made a fuss of her, then showed her dc2 without making her hold him etc. We gave her a present from him. We asked what she'd been doing in the time we were at the hospital. Dc1 suddenly looked like a huge lumberjack compared to dc2!
In my experience, some toddlers love babies and some aren't interested. Ours wasn't interested and it made life easier in many ways!
One thing you need to do is remember dc1 is tiny and doesn't know baby etiquette, it's easy to expect them to care about not waking the baby, or to care that you're tired or have birth injuries that mean it's hard to play etc - toddler social skills are still at sociopath level, they won't care but that's just what's natural for them.