Update README and add gitignore

Change-Id: I71d4204d5f852de87f9f92751017d0e6db53f220
diff --git a/README.rst b/README.rst
index 7ba5c33..18e3763 100644
--- a/README.rst
+++ b/README.rst
@@ -5,3 +5,11 @@
 Tempest Plugin for Horizon tests
 
 * Free software: Apache license
+
+Using
+--------
+Install this plugin in the same python environment as tempest.
+
+In tempest directory, run::
+
+  testr run tempest_horizon.tests.scenario.test_dashboard_basic_ops.TestDashboardBasicOps