Setting up Google Tag Manager (GTM)
Google Tag Manager (GTM) is a free tool that allows you manage and deploy marketing tags (snippets of code or tracking pixels) on your website without having to modify the code.
Set up time: 3 mins.
Difficulty: easy.
You need to take code snippet from your account and paste it in your website settings. Please, check out Google's original tutorial: Text tutorial or Video tutorial

Paste the first code snippet in your Website settings > Custom code tab > <head> custom HTML code:

Paste the second code snippet in your Website settings > Custom code tab > </body> custom HTML code:

Done! Now you can add tags in your GTM dashboard.
Set up time: 3 mins.
Difficulty: easy.
You need to take code snippet from your account and paste it in your website settings. Please, check out Google's original tutorial: Text tutorial or Video tutorial
GTM will give you 2 pieces of code:

Step 1: Place the <head> code
Paste the first code snippet in your Website settings > Custom code tab > <head> custom HTML code:

Step 2: Place the </body> code
Paste the second code snippet in your Website settings > Custom code tab > </body> custom HTML code:

Done! Now you can add tags in your GTM dashboard.
Updated on: 09/04/2021
Thank you!