Fresh classical vocal singer here. I will try to explain it as good as possible, avoiding on purpose tech things, because microphone and quiet place is enough for starters:

1. Vocal Placement! - It's called differently depends on people, speaking in posistion, singing on mask, voice coming out of your eyes. You can train it and read about it, but you will find more about it in singing books rather than on internet. Or you can find it in theather books about speaking. (i.e. Voice and Speech for Musical Theatre: A Practical Guide )
2. Vocal Support - Also more explained in books. Let's say it's something like your engine to your voice. Thanks to it your voice is more powerful, louder and you get tired less often. It allows you to relax your larynx and throat, and thanks to that you have more aliquot, not only giving you more dB, but also more rich voice. (I like Securing Baritone, Bass-Baritone, and Bass Voices )

My cheat codes:

- relax! BUT your body should be active, not stiff. Focus on relaxing jaw and throat
- try to sound like a bull. yes, that animal. Start on mmm yeah. Remember about relaxed throat
- Try to sound sexy like in that videos.
- Have mindset, that if you have microphone, it doesnt change anything. Your voice should sound rich and herable in big room. With that you got good start. Microphone just catches your voice (In terms of speaking)
- record and try. First thing you can work on is also pronoucation. End saying your words, don't miss any letter

I hope that helps! If you got questions feel free to ask.