Add GitLab QA documentation

[ci skip]

qa/README.md

@@ -16,3 +16,22 @@ against any existing instance.
 1. When we release a new version of GitLab, we build a Docker images for it.
 1. Along with GitLab Docker Images we also build and publish GitLab QA images.
 1. GitLab QA project uses these images to execute integration tests.
+
+## How can I use it?
+
+You can use GitLab QA to exercise tests on any live instance! For example, the
+follow call would login to the local GitLab instance and run all specs in
+`qa/specs/features`:
+
+```
+GITLAB_USERNAME='root' GITLAB_PASSWORD='5iveL!fe' bin/qa Test::Instance http://localhost
+```
+
+You can also supply a specific tests to run as another parameter. For example, to
+test the EE license specs, you can run:
+
+```
+EE_LICENSE="<YOUR LICENSE KEY>" GITLAB_USERNAME='root' GITLAB_PASSWORD='5iveL!fe' bin/qa Test::Instance http://localhost qa/ee
+```
+
+All [supported environment variables are here](https://gitlab.com/gitlab-org/gitlab-qa#supported-environment-variables).