Some of the Builder templates allow you to adjust the width of the content area of the website. The site width minimum and maximum will change depending on the template you have saved.
In the below example, the Walnut Street template is saved.
To access this setting, first click on the BUILDER icon then hover over SETTINGS and click on GENERAL.
The first option you'll see is site width. Enter an appropriate number then click on SAVE CHANGES.
Below is an example of what your page could look like on a laptop screen with a site width of 1000 pixels:
Below is an example of what your page could look like on a laptop screen with a site width of 1200 pixels: