On page SEO is very important in raising the SERP (Search Engine Result Position), You can create internal links in wordpress manualy in every post you, More internal links within a website that makes the website even stronger in the eyes of search engines, You can use the plugin to create an internal auto links, to make the internal links that are relevant to these post, there are two plugins that I normally use to create an internal auto links wordpress:
SEO Auto Links & Related Post
Like the picture above you can manually add keywords that want made into the internal links, with the format (Keyword, URL). Then in addition you can also create a related post on this plugin, by making a tick in the “Enabled related posts.”. The SEO ALRP is auto insert Features related post on single post, but you also can put the related post manually.
<?php if(function_exists('seo_alrp')) seo_alrp(); ?>
Add that code on your part that you want to display the related post.
SEO Smart Links
This plugin is already more popular than SEO Auto Related Links & Posts, but only complains on this plugin dedicated to create internal links on wordpress, Some settings on SEO Smart Links you should know.
I used to Allow Links to Self in the post. You also can create an internal links pad to give the check Allow Page Links to self in Pages, On Target in addition to giving the internal links on posts and pages you can also create an internal auto link to categories and tags.
You also can create custom Keywords, with formats such as SEO ALRP.