If you're looking for your Zynga user ID, there are a few places you can look. The first is in the settings menu of your game. To get there, just click on the gear icon in the top right corner of the game screen. In the settings menu, under the Account tab, you will find your user ID listed next to your name.
Another place you can look is on your Zynga profile page. If you go to www.zynga.com and login, then click on your name in the top right corner, you will be taken to your profile page. On this page, under the Info tab, you will find your user ID listed next to your email address.
If you still can't find your user ID, don't worry! Just contact Zynga customer support and they will be happy to help you out.