The idea is that category names should appear in the language of the page. Importantly, clicking on that category statement takes you to a list of similar pages, so you don't want dozens of English pages showing up on the same page . We have an (incomplete) list of translations, to ensure consistency, on Category_Translation,_Esperanto_to_Suomi(fi) - perhaps you could fill in the gaps?
The statement needs translation to look like "[[Category:دسترسی/fa]]" - the language extension being used so that languages with great similarities are not confused.
I do this in page http://userbase.kde.org/Welcome_to_KDE_UserBase but that page doesn't exist!: everything is correct? __________________________________ on same page I can't translate last section "If you are willing to contribute..." it say :Invalid token (badtoken) can you help me?
The redlink - yes that is to be expected. At first, all that is on that page is the auto-generated link to your page. What you should do now is, in Farsi, put on that page something like "on this page you will find Farsi pages about...." - take a look at the English equivalent category page. It doesn't need to be a direct translation of what's there, but it will give you an idea.
The only thing I can guess at is the possibility that you are translating a part of a link that should stay untranslated, such as "Special:mylanguage/Tasks_and_Tools" where only the "Tasks and Tools" after the pipe symbol should be translated. If it's not that, I'll try to get someone from the i10n team to look at it for you.