[Resolved] Display logged-in user's name

I want to display the logged-in user’s name and info on the front-end and I dont know how to make this work.

I already have the code below in my functions.php but I dont know how to display it on the front-end OR which hook to use:

// Get user name
function user_details() {
  $user_id = SwpmMemberUtils::get_logged_in_members_id();
  $fname = SwpmMemberUtils::get_member_field_by_id($user_id, 'first_name');
  $lname = SwpmMemberUtils::get_member_field_by_id($user_id, 'last_name');
  $user_name = $fname . ' ' . $lname;
  return $user_name;
}

thanks