Here you can find the instructions on how to change the banner image.
1. To change the banner image go to the Content > Blocks section.
2. Find the static block you want to change. Open the static block to edit (select Edit from the Action option dropdown)
To find out the particular banner static block name use the Template Settings table you can fin on the theme Live-Demo page. See the Template Settings footer link.
3. You’ll see the banner content field. Select the code which is responsible for the image display ( <img src=”{{media url=’wysiwyg/img_hom_10.jpg’}}” alt=”” />).
4. Delete the code and press the Insert Image button. Upload the new banner image (click Browse) and press the Insert File button.
The new image should have the same size as the previous one. See How can I find out the banner image name and size?
Remember to specify the image class, if any.
5. Save the block settings.