Updating primary and Rescue e-mails

To change your rescue email address, from http://support.apple.com/kb/HT5312 :

1. Navigate to appleid.apple.com using your web browser.
2. Click "Manage your account"
3. When prompted, sign in using your Apple ID and password.
4. Click Password & Security
5. You'll be asked to answer 2 of your 3 security questions before you can make any modifications. If you are unable to remember your answers, you can choose to send an email to your rescue email to reset your security questions.
6. After you've validated your identity by correctly answering your security questions, click Editto the right of your rescue email address.
7. Once you've finished editing your rescue email address, click the Savebutton directly below the email field.

I would like to ask why the option rescue email is not appearing I need to reset my security questions since i forgot those answers

If you aren't getting the reset link then you don't have a rescue email address on your account (alternate email addresses are different). You will have to contact Support in your country to get the questions reset.

Contacting Apple about account security : Contact Apple for help with Apple ID account security

If your country isn't on that page then try this form to contact Support : https://www.apple.com/emea/support/itunes/contact.html

When they've been reset you can then add a rescue email address via the steps in my above reply for potential future use : Manage your Apple ID primary, rescue, alternate, and notification email addresses