Navigate to https://opaclibrary.addu.edu.ph/?config=college and click the Log in link on the LS2 PAC home page.
You will see a Sign in with Google link on the login to your Account form, as shown below.

To set up your Google account and link it to your PAC account, click the Sign in with Google link. Once your Google account is set up, you must log in using your library account (Library ID/PIN or EZ Username/EZ Password) to link your library account to your Google account. As illustrated below, the Login to your Account form appears with the message, Your email [your email address] is not linked to your library account. Please sign in to link your Google account with your library account.

Once you sign in with your Library ID or EZ Login, a confirmation displays at the top of the screen, Your Google Account has been linked. When you log in to PAC the next time, click the Sign in with Google link and the system will log you in without the need to enter a Library Card Number/ PIN or EZ Username/EZ Password.
You will receive an email to the email address you specified on your library account (under Contact Information) informing you that your Google account has been linked to your library account. This is simply to ensure that you initiated the change.