If you select a customer from the Profile dropdown on Your Customer Profiles page, you can see a yellow banner with instructions depending on whether your customer provided one, more, or no supplier account owners.

If the customer provided supplier owner contact information, you can email them directly by clicking on the email address (one contact email) or on the send them an email link (more email addresses).

If your customer does not use a supplier information form, depending on their settings, you might be able to see the Edit button and edit your customer profile.