Home Page is the page with the list of your enabled customer portals. Taking into account that you can use only one customer portal (also no customer portals at all) this page can be optionally set up as the first one after login to the Customer Area. Even if not set up, it is located at YOUR_JIRA_ADDRESS/secure/hd-home-page.jspa
The page appearance is not much customizable so far, however, you can add your own banner here. The portal name and description go from the portals settings.
Navigate to HelpDesk Settings → Customer Area → Home Page
Upload the banner selecting it from your computer. The recommended size is full HD. The parallax effect will be applied automatically.
To set the home page as the start page after login to HelpDesk, select the relevant option in the General Settings of Customer Area.