1. To adjust the number of posts visible on the main or archive pages go to Settings > Reading.
2. Edit the Blog pages show at most field by entering the number of posts to be displayed, per page, on your site. Click Save Changes.
Display different number of posts per page in the archives
If you want to control the number of posts that appear on the front page, search results, and author, category, tag, and date archives, independent of each other, including specific archive use Custom Posts Per Page plugin.
