if you define in conf/zeppelin-env.sh
export SPARK_HOME=<PATH_TO_SPARK_DIST>
Zeppelin will then look in $SPARK_HOME/conf/spark-defaults.conf and you can define jars there:
spark.jars.packages com.databricks:spark-csv_2.10:1.4.0,org.postgresql:postgresql:9.3-1102-jdbc41
then look at
http://zepplin_url:4040/environment/ for the following:
spark.jars file:/root/.ivy2/jars/com.databricks_spark-csv_2.10-1.4.0.jar,file:/root/.ivy2/jars/org.postgresql_postgresql-9.3-1102-jdbc41.jar
spark.jars.packages com.databricks:spark-csv_2.10:1.4.0,org.postgresql:postgresql:9.3-1102-jdbc41
For more reference: https://zeppelin.incubator.apache.org/docs/0.5.6-incubating/interpreter/spark.html