On the left side tool-bar of your mobile editor you will have 3 options:
Once selected you will be shown different options that you can use to optimize your website for mobile viewing.
The Settings menu will let you reset your mobile content to match how your website looks in the PC Editor, this can be done clicking on Reset Page Content As PC.
You will also have the option to display your desktop site or mobile site.
You will also be shown a list of the elements that have been hidden on the mobile editor of your website, some elements will automatically be hidden as they will not fit on the page correctly when viewed on a mobile device.
The Layout menu will let you control Padding, Alignment and Spacing, For example if you would like to align your content to the left of the screen or centre, you will be able to do this here.
The Sections menu will allow you to review the different page sections of your website.
The Design Menu will allow you to change the background of your website, this will only change the background when your site is viewed on a mobile device. Your background in the PC editor will stay the same.