This is Finley from the Social Care team at Shopify. Thanks for your question!
I understand that when customers go to your homepage, you'd like them to see a video.
Which theme are you using for your website? If you're using a free Shopify theme, like the Debut theme, you can indeed add a video from within your Theme editor. To do so, click Add section and select Video. From there, you can re-order your Homepage sections, so this is the first section your customers see:
Next, you'll click the Video section and add your YouTube video link. If you'd like the option for it to play without the customer clicking the "play" button, you can make it a Background style video. Depending on your customer's desktop browser settings, as there are many ways for people to disable autoplay in their devices/browsers, your video may auto-play and auto-loop:
Though videos are a great way to engage customers, it's a good thing to be mindful when selecting the video you'll add to your website. Most popular browsers like Google Chrome will disable autoplay on videos that have sound by default. On mobile devices, autoplay is disabled to save users' mobile data. This article explains this further. Even without a browser or device disabling autoplay on videos with sound, many customers will automatically close a browser tab if they're interrupted by a sound.
If you're still working on creating a video for your products, we have an article on How to Make Online Videos that may provide you with some new helpful tips!
If there's anything I didn't cover today or details that I can clarify further, please let me know.
I hope you're having a wonderful day!