Thank you Tom for your info. Now I'm wondering if it's possible to limit add/ delete only to administrator. Staff can only see and do research. Thank you

You can make code effective only to admins by enclosing the code with if ( $sys->IsAdmin() ) { like this

<?php if ( $sys->IsAdmin() ) {
//code to hide from non-admin
} ?>

If you want to show it to only non-admin, use this:

<?php if ( !$sys->IsAdmin() ) {
//code to show to only non-admin
} ?>