Thanks for writing in! I have checked your site and it turns out that you are trying to edit a Portfolio page. Please understand that you cannot edit any page that is using Layout - Portfolio page template because the contents of this page will be dynamically generated by the template and it does not display any contents that you will add in the page description.
If you want to add a hero image and some text, please make use of Revolution Slider. You can install it by going to X > Overview > Extensions. Once installed, you may create a hero slider and add it below your masthead settings. To know more about this plugin, please go to this knowledge base article:
To know more how you can use sliders within the theme, please check this out:
Hope this helps.