Docs: Update Google Tag Manager (#9757)

* update gtm docs

---------

Co-authored-by: Bijan Boustani <[email protected]>

contents/docs/libraries/google-tag-manager.md

@@ -4,33 +4,48 @@ icon: >-
   https://res.cloudinary.com/dmukukwp6/image/upload/posthog.com/contents/images/docs/integrate/frameworks/gtm.svg
 ---
 
-## Objective
-
-Integrating PostHog into your website using Google Tag Manager.
-
-## Why is this useful?
-
-[Google Tag Manager](https://marketingplatform.google.com/about/tag-manager/) helps you add tags into your website in a codeless way, for services such as marketing and analytics tools. 
+[Google Tag Manager](https://marketingplatform.google.com/about/tag-manager/) helps you add code snippets or tracking pixels to your website in a low-code way to send data to services like marketing and analytics tools. 
 
 It is an easy way to integrate PostHog into your website without having to update your codebase. 
 
-## Prerequisites
-
-To follow this tutorial along, you should:
+## How to add PostHog to Google Tag Manager
 
-1. Have [deployed PostHog](/docs/deployment) or be using PostHog Cloud.
+1. Get your [PostHog snippet](/docs/getting-started/install?tab=snippet) with your project API key and instance address from [your project settings](https://us.posthog.com/settings/project).
 
-## Step-by-step instructions
+2. Assuming you have already set up Google Tag Manager, go to your [dashboard](https://tagmanager.google.com/) and navigate to the desired account/container that is integrated with the website you want to add PostHog tracking to.
 
-1. Get your [PostHog snippet](/docs/integrate?tab=snippet) from your 'Project Settings' or the initial PostHog setup
-2. Access your [Google Tag Manager dashboard](https://tagmanager.google.com/) and navigate to the desired account/container that is integrated with the website you want to add PostHog tracking to
 3. Click to add a new tag:
 
     ![GTM Dashboard](https://res.cloudinary.com/dmukukwp6/image/upload/v1710055416/posthog.com/contents/images/tutorials/gtm/dashboard.png)
 
-4. On the page to configure a new tag, add your PostHog snippet as a 'Custom HTML Tag' under 'Tag Configuration'
-5. For the trigger, select the default "All Pages - Page View" trigger and then click 'Save' on the top right corner of the drawer
-6. Back on the main dashboard, click 'Submit' to update your website with the new PostHog tag
-7. You're done! PostHog is now configured for your website.
+4. Under **Tag Configuration**, choose **Custom HTML** and add your PostHog snippet.
+
+    ![PostHog snippet](https://res.cloudinary.com/dmukukwp6/image/upload/Clean_Shot_2024_10_29_at_16_25_01_2x_1e99eea9d1.png)
+
+5. For the trigger, select the default **All Pages - Page View** trigger and then click **Save**.
+
+6. Back on the main dashboard, click **Submit** to update your website with the new PostHog tag.
+
+7. You're done! PostHog is now added to your site and autocapturing data like pageviews and clicks.
+
+> To confirm PostHog is configured correctly, visit your website and then check if the events from your session appear in [the activity tab](https://us.posthog.com/activity/explore). It may take a few minutes for events to appear.
+
+## Using all the features of PostHog via Google Tag Manager
+
+PostHog works the same via Google Tag Manager as it does via our snippet directly. This means you can use all of the features like session replays, surveys, and more without additional setup. 
+
+Some of these do require calling PostHog, which you can do by checking for the window's `posthog` object and calling any of its methods. For example, you can capture a custom event like this:
+
+```html
+<script>
+  (function waitForPosthog() {
+    if (window.posthog) {
+      window.posthog.capture('hello');
+    } else {
+      setTimeout(waitForPosthog, 100);
+    }
+  })();
+</script>
+```
 
-> To confirm PostHog is configured correctly, visit your website and then check if the events from your session appear in PostHog. Note that this may take a few minutes.
+You can find the full list of methods in our [JavaScript Web docs](/docs/libraries/js).