Link back to mainpage

Maybe it’s a really stupid question, but I’ve been searching for a while now and I can’t really find the answer anywhere…

When someone clicks on my post the post appears but there is no button back to the mainpage of the blog. I know that people can use the back button of their browser, but still.

I have the same problem with my pages. Have several of them, but no link in the sidebar to get back to the mainpage.