Practice, practice and practice.
Practice conversing with your family and friends.Just talk about their day, plans for the week, how was their week, what they got up to, how's everything.Did they watch the sports game, watched any movies, how they found it, etc.
Talk to people at the bus stop, the shop staff, anyone, ask about their day, their plans anything.
Once you start talking, you will find about the other person so you can talk about their work, hobbies, etc.
Joining clubs that are fun and interesting with you will help.
Their are good books out there, two I would recommend are: How to talk to anyone and How to win friends and influence people.