In the admin Marketing > Banners

Name The required name of the banner

Store If you have a multi-store version, which store front can accept this banner image

Pos Sequence number of displaying multiple banners on the site from 0 onwards

Type Either an image or text banner

Image Upload the banner from local, server or URL

Open in new window Have the banner link to a page in new window or not

URL The URL if link from the banner is required

Creation date When banner created

Status Active, Hidden or Disabled

And select Create on the menu to save to the banner list.

You will then need to add the banner to the home page block.

In the admin Design > Layouts > Homepage

You will need to find the banner block in the page layout, this should be titled accordingly.  Select the cog icon on the block.

Select Content and add your new banner, then save.