You can effectively unblock YouTube by contacting your system's administrator. No website is blocked by default; If a website is blocked, it is because a system administrator has blocked it.
The best method for unblocking a website is specifically correlated to the tool with which it has been blocked. But, in all cases, users will first require the correct credentials. There are a number of ways to block access to web addresses, including using a router's settings, third-party software, or the computer's hosts file. A valid username and login are required to change the settings on a router or blocking software, and administrator privileges are needed to edit a computer's hosts file.