You describe the videos you want once, and Chillframe keeps making them and posting them to your connected channel. That's a Series: a recurring publishing schedule with a fresh video in every slot. Each post shares the mood rather than repeating it, so the music and the scene are new every time. Series need a plan, and how many you can run at once depends on which one: one on Starter, three on Creator, and no limit on Pro or Max.
Start at Series → New series. The first card is Theme: a Series name, and a Theme brief describing the scene and mood, which then applies to every post. If you'd rather pick than type, Starter presets writes the brief for you, and all 61 presets are in there.
Next is Look & sound. You choose a Video type, Lite or Plus (Creator, Pro and Max allow you to make motion videos), and Plus adds a Loop duration and a Resolution. Under Audio you pick Instrumental, With vocals or Ambience only, then an Audio duration of up to an hour. If your channel is for sleep or study, Ambience only is the one to try.
The last card is Cadence & destination: your Posting days, Time of day and Timezone, the Destination channel, and Before each post publishes, which is either Auto-publish or Manual approval. As you fill it in, the builder tells you how much of your monthly usage the Series would use. If the schedule needs more than your plan gives you each month, a More than your plan covers warning shows up, and you can change the schedule or move up a plan before you create it.
Your first post is held for review whichever of those two you pick. It starts rendering, and uses its usage, as soon as you create the Series. Nothing reaches your channel until you press Approve & start schedule on the series page. For when renders start and when posts go live, see How the posting schedule works.