How do I create a Blog Page?

Navigate to Pages > Add New. 
Give your new page a name of Blog, Journal, or something similar.
On the right under Page Attributes, you'll see a Template dropdown. You'll select Blog Page from that drop down.

NOTE: If the Blog Page Template is not available, select "default" and continue with the tutorial.

Classic Editor: Click the "screen options" at the top of the editor. Continue with the tutorial below the Gutenberg image.

Block Editor (Gutenberg): Click the 3 vertical dots in the top right of your screen and from that drop down, select Options at the bottom.

From the panel that pops up, be sure Custom Fields has a checkmark next to it.

On the left side, under the post content, scroll down until you see the Custom Fields section.
Select the Enter new Option.
Enter query_args in the name field.
Enter showposts=6 in the value field.

Publish your page. Now all your blog posts are on the blog page!

For more information about how to use query_args, see this article by Studiopress that shows how you can include/exclude specific categories.