If you are joining a meeting in Chrome, Chrome Mobile, Firefox or Opera, you will not need to download anything to experience most features. To use IE11 with SuiteBox, you will be asked to install a plugin as you enter the meeting.
In order to screen share from Chrome or Firefox, you will need to install a (free) browser extension. To download the extension, simply join a meeting with another person, click Add File, then Screen Share. The browser will then guide you through the install process. Simply refresh your page afterwards, and you're ready to use screen sharing in your SuiteBox meeting.