How do I merge Dolby Atmos audio files into films edited in Premier Pro??

I am an audio engineer. The studio I work at has an incredible Dolby Atmos room and that's where I spend most of my life these days. I have no questions about creating Dolby Atmos audio content. However, I have no idea how its merged with video and I really need to know.  I've been creating the audio, shipping the files off to the client when finished, and haven't run into any issues yet, but I see multiple ways that not knowing how my audio files become part of a video file after I'm done could become a problem.

Let's say a videographer I know shoots a music video for a client of ours. That client has paid for a Dolby Atmos master of that song and would like to have the Dolby Atmos music master be the audio for the video. How would I bring the Atmos audio into the video and render a video that has Atmos audio?
OR Let's say I get a client who's just shot a film. He's paying us to mix the audio and would like us to render it in Dolby Atmos. He's new to Atmos and doesn't know much about it other than how good it sounds when he's watching movies on Apple TV+ or NetFlix. He works on his film in Premier Pro. How do I walk him through importing the file I mix for him that I've rendered in Atmos? After bringing in the audio? How does he render it with the Dolby Atmos audio track?

We work in Nuendo, which has served us well thus far. It allows me to import the video and I'm able to sync to it just fine. However, I've never actually merged the video and the Atmos audio. I only render the audio and have nothing to do with putting them together. If someone calls and says I messed up syncing them, I'll have to take their word for it and am limited in my ways to check because I can't put the Atmos audio in the video myself.

Yes, technically, I can import the video into the MP4 and render them together, but I've never been able to make that video file myself. I can't do something as basic as that even. I can say "Here's a link to what Dolby says you should send me so that I can make you an MP4" obviously, but I'm an absolute rookie on the video side. 
I did sit in on video/film classes in college, when I was studying audio, to meet people on the video side of the business and made some connections that have paid off many years later. I learned a whole lot about light, editing video, and plenty of creative stuff, but I learned absolutely nothing about what now seems like the only thing I should've paid attention to- mergin my audio with video.

Can someone please help. Video is your domain and I yield to the experts on this matter.