You have to immerse yourself in the uncomfortable situation so it becomes less of an issue as you become "hardened" to it. You have to sit in the awkwardness.. just sit there and soak it up and remind yourself that "it's all good", smile to yourself. Life is temporary, not infinite, so there is no point in being weighed down by such fear. You have the power to change this.
You find things to talk about - you can ask questions, you can learn and you can teach, you can say whats on your mind.. the more you make an input, the easier it becomes.. more "threads" start to be found with the person or people you are talking to. You can just ask a question and listen, you can let others do the talking if you wish, then talk when you feel the need. You can talk about things that interest you, or you can ask questions and talk about things to learn from others.
It is like jumping into the deep end of the pool for the first time. At first you resist with everything to do it. Your body is resisting this social situation and creating tension. But once you jump into the water, it becomes easier each time after. It is the same kind of thing. Like building a muscle. You are weak to begin with, and with the repeated action and movement you are able to strengthen. So it is this experience over time that enables you to learn and grow.
If you have any questions then just let me know