This is an important step within WordPress to define which of your pages displays as your homepage (front-page) and also the blog homepage (posts page). To do this go to Settings > Reading.
If you want your blog posts to be your homepage then leave the default Your latest posts option selected.
Otherwise if you want to set your portfolio page (or any other page) as your home page then select the second option and from the drop-down choose your desired page for Front page.
Do the same for the Posts page option, but in this case you need to select the page you have created for your blog.