The search terms admin page allows you to pick the search terms you like to monitor positions for in Google and Yahoo search engines. Those search terms will be monitored weekly (registered users only).
To add search terms to the list of search terms you want to track use either the free text form or select from the suggested search terms list (which is taken from your meta keywords and title tags). In both of those you need to press the relevant "add" button to add them to the chosen search terms to track which appears in the upper table.
To remove search terms from the chosen search terms list you can use the delete button in the upper table. You'll need to press the delete button in the row where the search term appears.
Both adding and removing search terms from the chosen search terms list which appears in the upper table will not affect the actual search terms list that the sheerseo uses until you press the submit button. So, when you are finish creating/editing the search terms list don't forget to press the submit button below the upper table.