You should e-file your return as it will be processed more quickly and the IRS already has a copy of all W-2 and W-2C forms you have received. The IRS also encourages taxpayers to file electronically. If you do decide to mail your return then you do need to send a copy of all W-2s and W-2Cs.
Please view the IRS link below for more instructions on when, where, and how to file.
https://www.irs.gov/taxtopics/tc301
