While the accepted answer is correct, that method has been deprecated. Topic configuration should now be done via kafka-configs
.
kafka-configs --zookeeper localhost:2181 --entity-type topics --alter --add-config retention.ms=1000 --entity-name MyTopic
Configurations set via this method can be displayed with the command
kafka-configs --zookeeper localhost:2181 --entity-type topics --describe --entity-name MyTopic