Post formats are set according to the type of content in the post.
Post format in WordPress
WordPress offers 8 types of formats by default: normal, note, image, video, audio, quote, link and gallery.
The offer of individual types of formats depends on the used WordPress theme. If your WordPress theme supports post formats, you can find their menu on the right side of the page for creating and editing a post. Not all topics have a formatting toolbar. You will find the necessary tools for inserting a specific type of post in the menu page for inserting a new post.