Tina demonstrates how users can create custom certificates with specific values and access them in a client portal. She guides viewers through the process of using the Certificate Builder within a membership site, highlighting how to import custom values, add text such as the current date, company name, student name, and course title, and then save the template. Additionally, Tina shows how to send a test email to preview how the certificate looks, as well as how students can download their certificates from the client portal, making it easier for them to access their achievements without sifting through emails.