You should have enough posts for this to work, Precious, so click on User CP (user control panel) at the left end of the black navigation bar above. If you want your picture to show on all your posts, scroll down to Settings & Options, click on Edit Avatar & follow the instructions.
The other way to display a picture is in your profile. If you want it to show only when people check your profile, then go to User CP again, and the third option under the Your Profile heading is Edit Profile Picture. Click that and follow the instructions.