Connecting your Gmail/Google Apps email account will connect both email and contacts to Contactually.
1. Go to Contactually's Settings and click Email Accounts on the left hand side.
2. Under Connect Your Email Account, click Gmail.
3. Log in to your Gmail account or select the account you want to connect if you have multiple Gmail accounts. 
4. Grant Contactually access to your email and contacts. This is required in order to sync your emails and log activity with your contacts, but Contactually will never send or delete emails without your permission.
Two-factor Authentication and Gmail
Using two-factor authentication (2FA)? If you use 2FA to log in to Gmail (this may be required by your organization if you are using an enterprise account), you may need to generate an app-specific password to use in place of your regular password when logging in. If you are certain your password is correct but getting errors, try this approach. Learn more about Gmail app-specific passwords in this Google support article.