Form 2210: Requesting a waiver of underpayment of estimated taxes due to retiring. The IRS instructions say to attach verification of retirement. How do I do that?

The IRS doesn't allow attachments to your tax return to be e-filed. You'll have to mail in your tax return. 

The IRS does allow specific documentation to be mailed in after you e-file and your return is accepted by the IRS. However, Retirement verification is not one of the specific items. Please see Form 8453 for the allowable attachments.