To install a widget on your WordPress website, the first thing you want to do is add the domain to Authorize Websites list. You can find it under the Setup tab of the widget settings, or in Settings > Growth Tools.
You can install Insert Headers and Footers plugin that allows you to manage your <head> scripts. On your WordPress Admin panel, go to Plugins > Add New, find the plugin and activate it.
Once it's done, head to Settings and select the plugin. You will find the sections Scripts in Header and Scripts in Footer.
The first section is where you need to insert the copied JS Snippet:
NOTE: You must insert the JS Snippet only once.
If it's an Embeddable widget, you will also need to insert the embed code:
On your WordPress Admin panel, head to Posts on the sidebar, choose the post you want to have your widget in and insert the embed code as HTML where you'd like it to be displayed. Below is an example of how you can add Checkbox widget.
Update the post, make sure the widget is activated in ManyChat and check out your website:
And voila, you're done!