I appreciate that you have let us know which theme you are using on your online store! Looking into the Dawn theme, I noticed that changing the width of the text is not available using the Theme Editor. However, you can make a change of coding to the theme to have it displayed as you would like. Since the Dawn theme is designed and supported by Shopify, we can use free design time for Shopify themes to have our internal team make the changes on your behalf.
If you are interested in using the design time, you will need to login to your store using the Contact Us page. This will allow us to securely verify you as the store owner before speaking directly with a Support Advisor about the changes you would like to see.