McAfee SiteAdvisor has been disabled on Firefox browser, how do I enable it again?

That is why i went back to firefox 4,downloaded and install firefox 5 and lost most of my addons good thing i set a restore point before installing fiefox 5 ,check at the mcafee website for update , i haven't check because of other issues with one of my pc's and WOT is worthless.you can't enable it again firefox 5 will just block it