How can I make the faculty/instructor display alphabetically?
This theme-template is using the following parameters to display users (as seen here http://polytechnic.themeisland.net/theme-overview/faculty-members/):
'orderby' => 'display_name',
'order' => 'ASC',
If you would like to set this to something different, you'll need to use a child theme to alter this since order and orderby are not options included in the theme.
Support Policy | Articles | Standard Troubleshooting Steps | File a Support Request
What template should I write that code?
Again, as I've mentioned in other tickets, this is beyond what is included in theme support. But if you are going to alter this, template-faculty-grid.php