How to add Meta Tags and Custom Scripts
You can easily add custom scripts, Meta Tags, and other code to your store in your Store Settings.
Simply go to your store admin area, and select "Settings -> Store Settings" in the left menu. You can enter your scripts and Meta Tags in the "Header Scripts & Meta Tags" box.
You also have a separate box for "Footer Scripts".
Meta Tags are sometimes used for verification (e.g. in Google Search Console) and custom scripts can be for many things, including website analytics (e.g. Google Analytics).