Before upgrading to the next release, you need to upgrade to the latest minor version of the actual release. For OpenShift 3.6, you can find the different errata updates at https://docs.openshift.com/container-platform/3.6/release_notes/ocp_3_6_release_notes.html#ocp-36-asynchronous-errata-updates.
The procedure to upgrade to the latest minor version is the same as upgrading to the next release. As our lab installation is already on the latest minor version of OpenShift 3.6, we can upgrade directly to OpenShift 3.7.
End of Lab 7.1