Have you fully setup the Quota Manager screen:
The Pages Remaining (Page Quota) field shows the total number of pages that a user is allowed to print, in other words, their Page Quota. This is controlled by the Edit Quota dialog and the Add Pages dialog. When an account is set to "Track usage", and "Deny printing when Page Quota is exceeded" is NOT enabled, this field will display "Tracking Only" as the user will never be stopped from printing. If there are different settings for each printer, this column will display "Varies per printer".
The Scheduled Updates column shows an the current schedule for updates to the Page Quota amount. For example, "5 Pages every 10 days". As in the Pages Remaining column, this column will display "Varies per printer" if there are different settings for each printer.
The Printers Tracked column shows the currently selected printers to be tracked, or "All Printer" if all printers have been selected.
The Restrictions column shows the current restrictions applied to this account. The possible settings are:
None. No restrictions are set on this account.
Page Quota. The "Deny printing when Page quota is exceeded", option is set.
File Title. The "Deny printing based on the file title", option is set.
File Size. The "Deny printing if document size?", option is set.
Selecting users is very easy, simply click on the user and use either the Shift or Ctrl to multiple select more than one user. When more than one user is selected, both the Edit Quota and Add Pages dialogs are accessible and will operate on all the selected users.