Help with floor jack, leaked and won't pump?

ok so thanks for all your help. I found the fill hole, just a small rubber cap covers it. I bought some jack oil for $3.99. I was able to remove the piston thingy that sits beneath the handle, it just came straight out? I replaced the oring and plastic lock ring, and put it back in and put it all together. Works. Now want I dont know is why it leaked? I am thinking I may have stored the jack upside down (it goes in a case) and so maybe that is why the oil all leaked out. Will keep an eye on it. thanks