After you log in, you will see your username in the top right of the page. Click on that then go down to Account Settings > Social Networks. From there you will have the ability to connect to your respective accounts.
It can also be accessed from your profile page. On the right column, there are links. Click the 'Account Information' link, and you will be taken to the 'Edit Meber Account' page where there is a dropdown under the heading. Select Social Networks under the dropdown.