OID Interest would be shown on your 1099B statement that you get from your investments. Some 1099B do not have this OID. OID usually show up in a separate category underneath Dividends and Sales of Stocks. It could be on the 2 or 3 page of your 1099B.
You do not have to do this for every tax free bond that you own. Just the total as shown on your statement under OID category.