HOW TO LIMIT NUMBER OF DISPLAYED POSTS IN WORDPRESS

It's totally easy and is almost clearly written in the Wordpress documentation. I will go straight to the point.
You will have to know a little bit of PHP. In your themes folder, open the index.php file. In the file you will find this code(without the curly braces):

{ if ( have_posts() ) }

 this code queries your database for posts with the default setting from your Wordpress Dashboard.
Just before the code(without the curly braces), input this code to modify the query:

{ $query = new WP_Query( array( 'posts_per_page' => 4 ) ); }

"You can change the number of posts that suits your design."

Then you need to modify further. Change the following.... 

{ if ( have_posts() ) } to { if ($query->have_posts() ) }

{while ( have_posts() )} to { while ( $query->have_posts() )}

{the_post()} to {$query->the_post()}

 So that's all you need to do Happy coding :)