If you are eligible, you will need to file an amended tax return (Form 1040X), for the tax years to which this pertains, in order to claim a refund. Generally, you have 3 years to file an amended return in order to receive a refund. To amend your returns, use the following instructions: https://ttlc.intuit.com/replies/3288565
The following IRS link provides additional information about this Special Tax consideration for veterans.
https://www.irs.gov/individuals/military/special-tax-considerations-for-veterans
