When in OptimizePress 3 Builder, you have an option to edit the page on Mobile, Desktop and Tablet mode.
1) Open or Edit the page using OptimizePress 3 Builder. You’ll then find a ‘Device Preview‘ icon at the upper-right side of the screen.
2) Hover over the mouse pointer to the ‘Device Preview‘ icon. You will be able to select from the available options: Desktop, Tablet, Mobile
Click on the device mode you would want to edit your page with and start editing from there.