Location: Appearance → Customize → Global → Layout → Container
ColorMag Theme allows you to adjust the width of your overall site container. Basically, a container is an area where the content gets displayed. You can enter a number straight into the field or use the slider to change the width in pixels. (Available in ColorMag Pro)
Below you can check the images displaying the site layout when adjusting various container width:
Container width on 1346px
Container width on 857px