How do I file WC-3?

In order to file your Form W-3C, you would need to use "Intuit TurboTax Quick Employer Forms". I am attaching a post from user KennethB for your reference.  Click here: W-3C 

Here is also a link to the IRS instructions:

https://www.irs.gov/pub/irs-pdf/iw2w3.pdf

Did your employer give you a WC-3?  Check with them.  Maybe they gave you the wrong copy.  They are suppose to send that to the IRS.   Your copy should be a W2-C.