By "Enable iSCSI Storage Adapter" you mean to go to "Configuration -> Select Storage Adapter - > Click on Add button on top and select iSCSI storage adapter ...... RIGHT ?
Yes, exactly.
After you add the sofware iSCSI initiator, you will need to bind the vmk networking you set up earlier to it. Check out:
http://pubs.vmware.com/vsphere-51/index.jsp?topic=%2Fcom.vmware.vsphere.storage.doc%2FGUID-8AE88758-20C1-4873-99C7-181EF9ACFA70.html