How would I request issuance of awards for my grandfather?

Hope this helps. I've thought of doing same for Dad. Got his records years ago. It's nowhere near Stolen Valor to add the "been there" campaign awards. If his records uphold assignment to a unit that received a Unit Citation during the timeframe he served, that's good too. Any personal awards should be scrutinized. If the DD 214 says he rates any of these, that's solid. The rest requires a little research and honesty. Division or Regimental patches, rank, marksmanship and similar are a given. It's supposed to be an effort of respect toward the member, and anything other than an honest effort diminishes that respect. IMO. https://www.archives.gov/veterans/military-service-records

You can request the OMPF or in some cases you may have to use the Freedom of Information Act (FOIA) for info.
https://www.archives.gov/veterans/replace-medals

Start with the branch of service Grandfather served in, all branches have a personnel center that generally have records of personnel that served. Unfortunately in the Armys case a fire in the personnel section dating back to ww2 destroyed a number of files.Any paper work that you can find through family history that survived will be helpful ie
Social security #, a draft registration, his deployment documents, anything that he was issued.
Contact information from personnel centers can be found on line!!
Good luck with your hunt, you won't believe the adventure you are about to embark upon.
Long story short, I found a lot of information about my Grandfather (ww1) on ancestry.com!! After some months more than a year, I now have all his awards and decorations, duty uniform!!