Install the global site tag

You need to set $wgPageViewInfoGATrackingID to the ID of the Google Analytics property to which you want to send data to send event data to Google Analytics. (See the document for details)

Create a service account and enable the Analytics API

You need to create a service account and enable Analytics API to use PageViewInfoGA. See the document for details.

Configure credentials

You need to set $wgPageViewInfoGACredentialsFile to the path to your service account credentials you have downloaded in the previous step.

Configure profile Id

You need to set $wgPageViewInfoGAProfileId to your profile Id(View ID).

(Optional) Create and Use Custom Dimensions

There is not yet a guide for creating custom dimensions on Google Analytics web interface for this extension. See the document on Google instead.

After creating custom dimensions, set $wgPageViewInfoGAWriteCustomDimensions to valid array.

// Default to:
$wgPageViewInfoGAWriteCustomDimensions = [
    "dimension1" => "mw:page_id",
    "dimension2" => "mw:page_title",
];

Finally, you can use the custom dimensions.

$wgPageViewInfoGAReadCustomDimensions = true;