Settings can be accessed from the Materia profile page. First, open the profile page by first clicking on your name at the top left of the page, then click on the Settings link in the left side under your large avatar.
By default, notifications are sent when a widget is shared with you. To disable this feature, uncheck the Send me an email when a widget has been shared with me option.
By default, Gravatar is used as the provider of user icons for Materia. Gravatar associates an email address to an image (or, a gravatar). To set up or change your Gravatar settings, visit their service at Gravatar.com.