The following link will bring you to your profile in customization mode. When the page loads, the twitter module settings will appear. Simply fill out the settings in the settings box, then click "Save".
Add the Twitter Module to your profile:

Please Note: If you have a custom page setup, you will need to manually add the twitter module to your userpage. This can be done, by going to Customize > Page Setup, and pasting [mod:twitter] into your page setup. This is a standard userpage module so you can add it wherever you want.
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And, good work you stealthy devs, we love you.