Remove the template function that displays it from your sp theme. Look in spFoot.php and I think you will see it.

As always, strongly recommend having your own theme vs editing ours. See:

http://codex.simple-press.com/codex/themes/theme-basics/creating-a-theme/

That would be done by editing the spFoot.php file in your themes /template folder.

To completely remove it you need to find.

        sp_NewMembers(‘tagClass=spLeft spNewMembers’, ‘Newest Members: ‘);

        sp_InsertBreak();

and delete or comment out those two lines. It is recommended that you create and use a custom theme when you start doing things like his so any new updates do not overwrite your changes.