If you already have Google Tag Manager added to your site, installing the Plannit scripts for the web integration can be done by adding a Custom Tag for the Widgets and Bot (no matter what CMS or website host you have).
In Google Tag Manager, go under Tags, click New to create a new Tag:
Click Tag Configuration and choose Custom HTML as the tag type.
In the HTML field, enter your Script for the Widgets and the Bot, like below :
Scroll down and click Triggering, then choose All Pages
Enter a name for your Tag, like Plannit Widget and click Save
Submit your changes and you're good to go.