Where can I find c3 portal?

First of all they will have to download the Opera Mini 5.1 from this link, it is important to mess your browser to the phone's micro SD but do not run.

If you have already tried the steps that go about in many forums and have not been able to solve the problem, I suggest this: Reset your phone to factory settings, they will have the option settings, or just all. The best way is to reset everything (twice I found that if they do this, the tutorial works perfectly).
Enter menu - settings - Settings - personal settings - options - Add New - web - using access point .-- no pref
They return to Menu - Settings - settings - settings config.pro--personal adjustment

They return to Menu - Connectivity-wlan - Internet connection - ask first (with this the phone will ask you what network you connect, thus avoiding the collection of telcel).

They return to the Menu - internet - web settings - settings configuration - configuration - personal adjustment
Now we just connect to your wireless network in menu - connectivity - wlan - wlan available, and then open the menu operates - applications - features - memory card and navigate freely.

After researching for a while, I could find another solution to the problems of Youtube ... it is a browser called 'bolt', quite impressive that gives us the opportunity to sail from our c3 with a much better experience as we display pages in their original format and size we can move to fit the screen of our phone (forget about zoom and be working with opera mini) ... But this is another browser goodness, you have installed a web application that allow you to watch videos without problems, as has a video player 'own' that will give us a connection to watch streaming videos without any difficulty, you can enter youtube page 'original' and see the video without the need to enter mobile web.