Changing Width of Post in Heatmap Template

Does anyone know how I can change the width of a post in the Heatmap template? I feel like the post goes across the screen too far making it to hard to read and follow.

I tried going into the style.css and changing some numbers there but that changed the width of the template instead of the width of the text’s post. Does that make sense?

Can anyone, please, tell me if there is an easy solution for this?

Thank you for any responses in advance!