When registering, the first verification you will make is age verification. This is a basic tick-box, but in some places, viewers are requested to make further age verification.
You will next verify your email address. That will take you onto the rest of the verification, where you upload a photo ID to verify yourself and then with a liveness check. This is a video recording which will grab 4 images from different angles to verify you with your documentation. The verification system will check those images against the image on your photo ID.
You will then need to verify payments. This helps your future payments work smoothly. This can be done at the registration stage, but if not, it must be soon after your first payment or payments are made. You can contact support to help with that.