Hi Mike,
If you click on the User CP link (towards the top of the page under the grey panel that say Welcome back), this will take you to your user control panel.
On the new page, there is a menu on the left hand side. Under 'Your Profile' there are a number of options. You can add you DOB by clicking on the Edit Profile link, and update your profile picture by clicking on the 'Change Avatar' link.
The Change Avatar link advises you of the maximum file size you can use, simply click browse to find your chosen image from your computer and then, once uploaded, the change avatar button at the bottom of the form.
Kindest regards,
Julia