Oh man, that's so great to hear! I am super pumped for you!

If I'm not mistaken, that starter pack comes with a pre-made adventure for beginners, so with your books you will probably be ready to go right out of the box. Traditionally, a party is 4-6 players not including the DM. However, you can have less or more; it's personal preference. For your first time, I would suggest at least two players and a DM, though I would shoot for 4 players. I have run "duets" in the past with just a DM and a player, these can be very fun but usually involve a little more work for the DM. Personally, I cap a playing party at 6 players. When there's more than that, i find it hard to keep session flow consistent. The current game I'm
DMing has 4 players.

I am truly excited for you! It's best to approach it all with an open mind and not be afraid to fail. Roleplaying a character takes some getting used to, and DMing definitely takes some time to get the hang of (it took me a long time to feel comfortable behind the screen). As you are the primary pusher behind playing D&D with your friends, don't be surprised if you end up pigeon-holed as the DM as well. I avoided this for the longest time, but now that I've finally given in, I feel right at home. But certainly let anyone try it out who wants to. An easy way to do this is a "one-shot," or a campaign that you only plan to let run for one session, so the new DM isn't intimidated. A one-shot is a great way to try out some ideas/mechanics, it's also a great alternative if you don't have all of your normal players.

Most importantly, just have FUN. Yes, there are lots of rules and stipulations, technicalities and balances. But, the ultimate rule is to have fun. The rules are there simply to quantify abstract actions into balanced math. But all that math be damned if no one is having fun. If your party is really into roleplaying, don't simply throw enemies at them every session. If they are new to D&D, you should probably lead with combat stuff and let the RP come over time. The whole game is a collaborative effort between the players and the Dungeon Master, and you are all there to have fun.

There is one catch. Don't be surprised if you spend all of your free time thinking about your next session!

Edit: oh yeah, and DICE! Most hobby shops have a bigass bucket filled with dice for a quarter each, always fun. Feel free to ask me anything about the game-- I'm always in the mood to talk D&D. And let us know how your first session goes!

As a beginner you could try joining up a party first to see what's what, here's the recommended reddit to find peeps. This is the most popular online tool used by people, although it's better to find a group first and then see what they're using \o/
Just tell your friends it's a game of pretend, don't bother with being overly strict with rules and stuff, because you might want to move on to a different rule-set depending on your player preferences, there's like classic D&D (with a few different editions), Pathfinder, Warhammer, Star Wars, LoTR etc. For the first few games don't worry about being the perfect rule enforcer, just try to make sure everyone is having fun with their characters and the world you put them in. Since you want to play with RL friends that will make your job a lot easier, you already hopefully know what they might like, will it be a dragon 🐉 they face or will they TPK 🎲 at the hands of a small group of random goblins 👺 Involve them in the world, the best games will happen when you went in with a plan to do X, Y, Z but your players or a specific troublemaker player decided to just go the other way or look in that secret crevice that you never even thought about, improv will make the games more enjoyable for you and them! Make sure there's plenty of snacks to go around, everyone has time to chill and most importantly ALL PHONES MUST BE PUT ON SILENT OR VIBRATE 😾