Note:- That you don't need to be LogOut otherwise the premium cookie will expire and its stop working.
1. First go to any of your desired site like filesonic.com or hotfile.com
2. Then click Ctrl+D in mozilla or
3. Click on bookmarks in mozilla, see the last page you bookmarked, right click on it & then go to properties .
4. On the location field delete all, copy the javascript text given from my blog (premium-info.blogspot.com) & paste in location field & then click on save button. (This is the onetime process of adding javascript to browser)
5. After the process is completed then open a new tab and goto your desired site like filesonic.com
6. Then click on the bookmark menu, you will see the filesonic.com in that menu & then click on it. When a prompt comes paste your working cookie there and click ok. another prompt comes, just click ok & see you got the premium if you entered a valid cookie.
Here you can also download the video and follow the step by step process.