If you have a registered Shopkick account, you won't lose your kicks by reinstalling the app. If, after reinstalling, you aren't already signed into your registered account, just log back in.
To log into your account, choose the method you originally signed up with (email, Facebook, or Google+) and follow the on-screen prompts.
If you forgot your login email address, email us and we'll look it up. If you forgot your password, request a reset link on the login page."