Once Livedrive Backup is installed and running, you can add any folder to the backup list just by right clicking on it and selecting Backup with Livedrive Backup:
Livedrive will then upload the contents of that folder in the background. In future Livedrive will monitor the folder and any files you add or change will be uploaded instantly in the background as you work.
Advanced users can easily manage all of the folders you want to backup by opening the Livedrive Settings screen in your Windows Control Panel, clicking on the Services tab and selecting "Select folders and files to backup". From here you can manually add and remove folders to your backup.