To enable Webalizer in Plesk please follow the following steps:-
1) Login to Plesk control Panel.
2) Click the "Domains" shortcut in the navigation panel.
3) Click the required domain name in the list.
4) Click on "Web hosting Settings".
5) Click the drop down box in front of "web statistics" ans select any one of the two stats
application avaliable. Click "OK" once you have selected the stats option.
NOTE:-If you select the accessible via password protected directory
"/plesk-stat/webstat" check box then you will be able to access Webstatistics
at the URL: https://your-domain.com/plesk-stat/webstat using your FTP
account login and password details.