If your asylum is granted in Greece, you will get a residence permit which is normally valid for three years. Some months before the three years pass, you need to apply to renew your residence permit, because without a valid residence permit you will face a lot of troubles. The Asylum Service has recently announced that all applicants whose residence permit will expire by 30th of June 2018, need to submit their application for renewal of the residence permit by latest 30th of April.
To do this, you need to send an email to firstname.lastname@example.org. This email needs to contain two things. First of all you need to send the filled in application for renewal. You can find the application here. And here you can find a guide how to fill the application in different languages. You also need to send in the email a digital passport type picture of you. You can find more information in the guide. Please read the guide very carefully and comply with all the steps suggested in it! If you need help with the application or the mail look for help at a community center or a NGO near you.