Human grade fish oil supplements are made from exactly the same ingredients (usually!) as the ones for dogs. But check ingredients to make sure there is nothing in there that shouldn't be, and can harm dogs....such as xylitol etc.
Pure fish oil is okay. But keep the capsules or bottle of oil out of the light, preferably in the refrigerator to prevent rancidity/free radicals, etc.
There is some information, and information about dosages here:
There is also some other information here:
Apparently it is not just a simple fix though, as regular doses of fish oil can deplete vitamin E in dogs, so that will have to be taken into account.
It also might be wise to discuss this with your vet?