I am new to BuddyPress so I don’t know which functions and variables to use here.
Read the codex – for example:
http://codex.buddypress.org/developer-docs/the-bp-global/
You could create a function in your theme- functions.php or in bp-custom.php
and call it from template files
and pass it parameters like allowed_users, etc.
Or you code hard-code something like this into specific template files.
global $bp;
$allowed_users_array = (1,4,5,7);
if (in_array($bp->loggedin_user->id, $allowed_users_array)) {
// Show page
} else {
// "You are not allowed to view this page" message
// or load a custom error page using locate_template( array( 'some.php' ), true );
// or redirect somewhere by using bp_core_redirect( );
}