What you have attached is for a student visa application and does not serve the purpose. Please do not submit irrelevant documents.
I am surprised that you are looking or a "format" of covering letter; just to submit your degree to your HRM Deptt for addition in your personal profile.
If there is a specified format, then ask your HRM deptt.; else simply write a fw relevant lines enclosing a copy of your degree (you may be asked to produce the original for verification purpose).
When you can post this query in CiteHR; I am confident that you can surely draft a suitable letter yourself.
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