I try to go to a custom page, but...
 

It just returns to the homepage. I did the links and everything right. But that stills.

So how you add an link to a custom page (made on "content") to the upper menu?

Umm a custom page, is it like a subdirectory? If so, you need to include an empty .htaccess file so it wont be routed back to Mysidia's main site.

Hm...not.
It's actually these pages you does at the "Content" section of the Admin CP.

Edit: Ah! I finally found what i did wrong.