Featured Image in blog post

Hi. Why is it the featured image in every post is not showing? how can I fix this? thanks!

Roots is a starter theme, so we won’t second guess how you would like to use things like featured images in your designs. You have to add it the template manually, as per the WordPress codex.

I already put the code for the featured image, how to resize it same width of the post page? I have sidebar on my post page so it will just be 3/4 of the width of a container on bootstrap

This isn’t a Roots question. Check out @Foxaii’s codex link above to read all about Featured Images. You’ll need to figure out the best thumbnail sizes for your particular setup.