Help With Static Page / Author/Date

possibly edit page.php of your theme, and add some code at the relevant location; example:

Last updated by <?php the_author(); ?> at <?php the_date(); ?>.

http://codex.wordpress.org/Function_Reference/the_author
http://codex.wordpress.org/Function_Reference/the_date

details depend on your theme.

editing Twenty Eleven directly is not revommended; consider to create a child theme for your customisation.
http://codex.wordpress.org/Child_Themes

in content-page.php, add the code for instance here after this line:

<footer class="entry-meta">