There are two ways in which you can add your Tracking Code on ClickFunnels:
All pages of your funnel
Copy your Tracking Code from the Hotjar admin.
Login to ClickFunnels.
Go to your funnel Settings and click on Head Tracking Code.
Paste the Hotjar Tracking Code.
Your Hotjar Tracking Code will now be present on all pages of your funnel.
Specific pages of your funnel
Copy your Tracking Code from the Hotjar admin.
Login to ClickFunnels.
Go to the Edit Page.
Click on Settings and select Tracking Code.
Paste the Hotjar Tracking Code.
Save your page or Update funnel settings.
Hotjar will then only be present on the specific page you installed the Tracking Code on.
It can take up to 24 hours for ClickFunnels to detect the Hotjar Tracking Code
ClickFunnels Tracking Pixel Guide can explain further.