The amended return mailing address for your area can be found by using the link here.
Include the Form 1040X, any documents that were added that include federal withholding and all W2s, then attach any schedule or form that was changed by the amendment. If you are not sure, you can send the complete new return behind the Form 1040X.
If you had to amend the state return as well you can find the address by selecting your state below.
https://ttlc.intuit.com/replies/3302452