Internal link building can greatly affect your SERPS for the keywords you are trying to rank for and give a tremendous amount of relevance to Google as to the main keywords of your website AND internal link building can also have a very positive affect on your Bounce Rate. You can read a simple step-by-step guide on Internal Link Building at: Internal Link Building for On-Site SEO. I would have posted it here but I added screenshots and illustrations that are helpful to the guide and so it is best viewed directly from the blog itself. Thanks, hope you find it helpful!