Not a teacher!
One reason for the lack of participation could be that their vocabulary is too limited to express themselves in more detail. The topic could be not very interesting for the students or they are just shy when they have to talk in front of a group.
Maybe you could start with letting them talk about an area of personal interest like a hobby or what they did on the weekend or during their holidays. You could divide the class into groups and let every student talk for a minute. If they can't speak for a whole minute the other group gets a point. If they make mistakes while talking don't interrupt them. Correct these after the student talking session. Don't ask questions. Let the students question each other.