Actually, it's quite easy. Find in your profile the "Upgrade" button. Choose the most convenient payment plan: monthly or annually and pay the invoice. After it will be confirmed, you will become a Certified User.
Find the “Upgrade” button in the Quick Menu, just click on it and follow the instructions. You need to know that it is a paid option and requires more documents to upload. In the Export Portal About section, you can find more information on all the benefits and documents you need to upload in order to upgrade your profile.