Not to worry! Military mail is not as complicated as it may seem.
You can still create your shipping label through the Kidizen app, just as you would for any order (no extra cost for a regular parcel), you'll just need to fill out a PS Form 2976-A Customs Form to go with your shipment. This form can be created online here: https://cns.usps.com/cfo-web/labelInformation.shtml
You can read more information about preparing your shipment for Military APO FPO and DPO addresses on the USPS site here: https://www.usps.com/ship/apo-fpo-dpo.htm