Disability retirement pay you receive as a pension, annuity or similar allowance for an injury or sickness resulting from active service is not counted as taxable income. This also covers VA disability compensation and pension payments, grants for a home designed for wheelchair living, grants for a vehicle if you lost your sight or the use of a limb, and dependent-care assistance benefits.
There is nothing to apply for. Leave these payments out of the income you report on your Maine return.
Your VA award letter showing the payments and what they are for.