Montezuma Theme – Plugin error messages

Hi – I’ve got Montezuma installed and am trying to use Plugins I’ve downloaded. I keep getting the following error messages:

Your theme needs to be fixed for plugins to work (Especially Floating Social Media Icon). To fix your theme, use the Theme Editor to insert <?php wp_head(); ?> just before the </head> line of your theme’s header.php file.

Your theme needs to be fixed for plugins to work (Especially Floating Social Media Icon). To fix your theme, use the Theme Editor to insert <?php wp_footer(); ?> just before the </body> line of your theme’s footer.php file.

Unfortunately, the header and footer codes don’t use those tags and if I just pop in the code, I get a white screen. Suggestions for how to fix this theme to accept plugins?

Thanks.