As the feature / hero unit widget is not a drag and droppable widget, you will have to add it to the twig file. This link will help you do this:
If you want a different image on every other page then you will have to do the following.
1.For every page you want a different feature image, you will have to create a new page type . i.e. for /contact-us you can create a file called contact.twig (initially copied from default.twig)
- Add the feature widget in the code of contact.twig, make sure you use a unique id for the widget, like contact-feature
- Add contact to the pageTypes in metadata.json (see Advanced Metadata ).
- In the page settings, via the Page Types drop down, you can should be able to select contact. This means that the page will start to use contact.twig for the page HTML. From here you should be able to see the feature widget and change it’s settings.