Android Signing - Just before you upload to Google Store you need a keytool - sign your apk file

For development you dont need but for for publishing (i.e. Android Market) you have to sign in your  apk file.

1) Locate the Publishing Settings under PlayerSettings
2) Create a new keystore by selecting a keystore name and password (confirm the password)
3) Select "Create a new key" under Key Alias
4) A new window opens; enter the necessary information.
5) Select the newly created key.
6) Build ( & Run); your app is now signed.

Dont forget your password. That is important. If you ever forget your password you cant upload your apk file later! Always remember the passwords; they are not stored with the project (for security reasons).