You can hop over to foursquare.com/settings to edit your account information including:

• Uploading a profile photo (this will be visible on your public profile page)
• Your full name (only your first name and last initial will display on your public profile page, your full name shows to friends and may show up if someone searches for your name)
• Your email address and phone number (only shared with friends if you have this option checked in the Privacy Settings section of foursquare.com/settings)
• Your location (city, neighborhood or whatever you feel like!)