If you are registered as an author and are logged on, you will have a ribbon with commands at the top of your browser window.
On that ribbon is a button that says ‘+ New’. One option in that button is ‘Post’, and that is the correct one to create a new blog article. Clicking ‘post’ opens the editor


You will see a place to enter a title and below that an area to add ‘Blocks’. Blog articles in WordPress are organized into blocks. There are several kinds of blocks that correspond with different types of content. Perhaps the two most important are the paragraph block and the image block. Heading blocks are also useful to make the article accessible. Here is a description of the blocks
To add a block, click on one of the buttons with a plus sign. The blue button in the upper left presents the most options.

