Then, in the options box on the left side, click on profile.
At the bottom of the page is where you add your birthdate. If you don't want your age shown, simply leave the year blank.
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You can also add a website link, things that intrest you, Your occupation, and any messengers you have.
Click submit at the bottom and you're done.
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Now, on your birthday, your name will show up in the birthday box at the bottom of the forum, and you should get an email.
Edit to add pic: