I can't find it anywhere on the website. Why did they not show it on the front page? 
On which site?
In the editor, the preferences are just here
On the community site, it would probably be here
Which will take you here
On the forum, you can go here to view your forum preferences, which have a lot more customization than on the community site.
but i can't do anything related to enabling JavaScript extensions on other projects.
The community site does not work. it only shows 'Change password' 'Change Email' or delete account. It does nothing.
That's all there is, there's nothing else you can do on the community site.
If that was what you wanted to know, you could have just said so in your original post. Enabling JS is in the Snap! settings 
menu. You have to enable that setting every time you load the project.