Without a link to your website I’m not sure exactly what you mean by the new post showing on the whole site, so I’m going to make some assumptions here.
WordPress shows the latest post on your homepage by default, so I assume that is what you mean by “showing on the whole site”. This can be changed easily by going to Settings > Reading on your admin panel.
The first option “Front page displays” has “Your latest posts” as the default (I’m assuming this is your case). Simply change that to “A static page” and select a page to use as your homepage under “Front page” and one to use as your blog page under “Posts page”.
My suggestion is that you create a page under Pages called “Home” for example, and select that for the frontpage, then create a page called “Blog” and select that for the posts page. You don’t have to do anything to the blog page, as it will automatically show your latest posts.
I hope this helps!
