Other participants can support your ideas by commenting on your idea or using the rating scale. Depending on your profile preferences you can edit your notifications.
To edit your notifications, click the drop down arrow next to your name and choose "View Profile." From there, the third tab labeled, "Preferences" will direct you to choose your notification preferences.
If you'd like to be notified when others support your ideas, turn the "Activity Updates" and "Comment Email" notifications on.