"I need to find a download file for the H2 XRD update." (Note: In this case, you are describing the type of file rather than using the literal name).
When referring to a specific file name or a distinct action like a download link, "the" is the standard definite article used to identify that unique item. Download File H2 xrd TO SILK.bin
The proper article to use before is "the." "I need to find a download file for the H2 XRD update
"Click here to get the Download File H2 xrd TO SILK.bin." Download File H2 xrd TO SILK.bin
"I have already saved the Download File H2 xrd TO SILK.bin to my desktop."
If you are referring to the action or the file as a general object in a sentence, here is how you would use it: