If you need to add the snippet code via Google Tag Manager, follow these steps:
1. Navigate to Container in the upper menu of your Google Tag Manager account. Then, click on Tags to the left.
2. Click New. Then, choose Custom HTML Tag and press Continue.
3. Paste Picreel code into the filed and press Continue.
4. Select All Pages to enable Picreel working on all pages of your website. Or choose the needed pages by pressing Some Pages. When it's all set, click Create Tag.
5. Give a good name to the new tag and Publish it.
Now, when you install the code of your Google Tag Manager, Picreel will be installed as well.