Add new fileAdd slides on enabling XCAMS

using-code-ornl-gov/README.md

+# Accessing code.ornl.gov
+
+You can access [code.ornl.gov](https://code.ornl.gov) with your UCAMS (three letter login) or, if you are a non-ORNL collaborators, you may use your XCAMS account.
+
+External collaborators can apply for XCAMS accounts at [xcams.ornl.gov](https://xcams.ornl.gov/xcams/).
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