How can you talk a lot in a conversation if you are not that smart?

It is difficult for me to fathom my recollection of previous occurrences that have caused me to think like this. An intense fear of socializing out of my comfort zone in an attempt of coping with my oblivious nature to speak, without fully thinking. Out of FEAR of doing this, I have CONDEMNED myself to the company of only my house and what lies within. How do I overcome this state of thinking so I can start going out and making friends?