Google Tag Manager helps you install & manage codes easily without a developer's help. It's free and it's easily integrated with Wix. Please follow the below guide to create and integrate Google Tag Manager with Wix. Note: if you already have a Google Tag Manager installed please skip to section 4.
1. Go to marketingplatform.google.com/about/tag-manager/ -> "Start for free"
2. Sign in with your Google account
3. Fill out the form details - Account name, country, URL, and choose Web under the target platform. Click create and agree to the terms and conditions.
4. Copy the ID as seen on the screenshot
5. Log in to your Wix account on wix.com
6. Click Marketing & SEO on the left-side menu
7. Click marketing integrations -> under Google Tag Manager, click "connect" and follow the guide on the Wix UI on where to paste the Google Tag Manager ID copied.