HubSpot's COS users may password protect Site Pages and Landing Pages as well as customize the look and feel of the password prompt page that visitors will see.To customize your password prompt page:

• Navigate in HubSpot Marketing to Content > Design Manager > and click the New Template button in the upper right-hand corner.

• In the template creation window, select Template Builder (or Code Editor if you wish to manually code a template) > System > and select Password Prompt Page in the drop down box that appears after selecting the System type. 

• Name and Save your new template.
• Once you've finished adding/editing/moving modules in your template as you wish, click the green Publish Changes button in the upper-right in template editor.

• To set your new password prompt template as the default for password prompt pages, navigate to Content > Content Settings. In the System Pages tab, use the Password prompt page dropdown menu to select your template. Click Save to take your changes live.