Hi, there.
This is Dallas from the Shopify Social Care Team.
If you go to your Store Admin (the page you see when you first log in) you should see a button that asks you to submit some documents.
It would look something like this:
When you click Submit ID you will be taken to a secure upload area where you can submit your ID. That area is fully secured for the safety of your documents and only our payments team has the ability to view the documents.
If you have any issues with the uploading process please do let me know.