If you've signed up for Podio with your Google account, you need to set your password in Podio before you can log in to our iPhone or Android apps.
To do this, click the profile icon in the top blue bar when logged in to Podio then go to "Account settings". You can set your password from there.
When you've set a password, you can then log in to the mobile apps (iPhone and/or Android) with your email and the Podio password.