Fill it in. Your own code is made when you pay.
Paste the link from the share button. e.g. https://youtu.be/…
For your analytics. A scan opens your link with these added to the end, so you can tell visits from this code apart. If your link already has a tag with the same name, this one replaces it.
Where people see the code. e.g. window-sign
What kind of thing it is on. e.g. qr
The campaign it belongs to. e.g. fall-menu
Pick a different kind of code