Break the ice by asking questions like "What do you do for a living?" or "What do you do as a hobby?", find common ground on something you're familiar with and talk about that. Ask them how life has been, or if they've met anyone recently or if they've read a good book or something.
You don't have to hold an intellectually stimulating conversation every time you talk to somebody, you can just talk to them. Sometimes all it takes is talking about the weather, or talking about cool cars or sports, if you're into sports. You could talk about how things have been looking up for you and your family, or if they're looking down, do the opposite. All it takes is a little bit of self-confidence and learning how to relax and have fun being a part of the conversation.
Nobody sane is going to judge you for trying to be a part of a conversation, either. If you say or do something awkward, just laugh it off, they'll follow along. If you have nothing to talk about, ask questions. Ask many questions, people like being asked questions.
