To create an Email Alert: Conduct a search by typing in a keyword and/or location and selecting what type of opportunity you're looking for (e.g. jobs, internships, etc.). Further narrow down your results with the filters listed on the lefthand side. When you're satisfied with the results you see, click the "Save this search" button to the right of the results.
To remove an email alert: Log in and click your name in the right hand corner. Select "Personal Settings" from the dropdown menu. You should see your email alerts listed there. Click "Unsave This Search" and you should be all set!