On creating a new News Item you will be presented with the Gutenberg editing screen.
The first thing to do is to enter the Item's title in the settings panel to the right - entering a heading as the first line of the item does not set the title.
Then start entering (you can cut and paste) content into the main panel where it says Add text or type / to add content.
The Gutenberg editor is described in the Edit with Gutenberg chapter.
At the bottom of the main editing panel is the More Settings section.
The Summary, Content Category, and Scheduling tabs are as described here within in the Edit with Gutenberg chapter.
The Placement tab looks like this (at the time of writing - 16/11/23)
Item Placement allows you to insert the item in that 'section' of the Latest News view. These will no doubt be refined.
In Which Letter allows you to insert the item into the General News (E-letter), the Children and Youth News (C&Y Letter) or Both.