You can use your certifications in many different ways (here is some inspiration), and one of the main ways to use it is on your portfolio page.
To display a certificate badge on your portfolio, go to your Certification section and enable the toggle next to the certification you want to show on your portfolio:
You can display as many badges as you like on your portfolio.
Once at least one badge has been enabled, your public portfolio will display a certification icon next to your name:
If visitors click this icon, they will see a list of one or more of your certification badges that you have enabled in your Certification settings:
Clicking on any of the badges will open the respective public certification page.