Actually Ambari support Namenode HA pretty well in version 1.4.1 or later versions. After we use ambari to enable the Namenode HA. every other components are configured by Ambari automatically. Please note I assume you are achieving the natural Hadoop HA, not VMware HA or Redhat HA.
If you want to configure it manually, here is some basic steps you can start with:
1. Shut Down the HBase Cluster
2. Specified the hbase.rootdir property in hbase-site.xml to the same value as dfs.nameservices in hdfs-site.xml
3. Start Hbase cluster.
Hope this helps.