How do I remove the Simple Catch footer

You’ll need to edit the file named ‘footer.php’ to remove the following code:

<?php _e( 'Copyright', 'simplecatch' ); ?> &copy; <?php echo date("Y"); ?> <span><?php bloginfo('name')?></span>. <?php _e( 'All Rights Reserved.', 'simplecatch' ); ?>

Be sure not to remove the preceding closing php tag ?> at the beginning of the same line. That needs to stay there.

Also remove this line:

<?php do_action( 'simplecatch_credits' ); ?>

If you want this modification sustainable, you’ll need to set one up. Otherwise your modification will be erased when the theme updates.

After you set one up, copy that footer.php file that you modified and paste it into your Child Theme.

That’s it.

Also any PHP file you want to edit in the future (apart from functions.php) copy it and paste it into your Child Theme directory.
CSS modifications can be made in your Child Theme style.css file.

See http://codex.wordpress.org/Child_Themes#How_to_Create_a_Child_Theme