How to check the hydraulic fluid on a ford 720 loader?

[Frankdozer]

I have a 1963 Ford 4000 Industrial Tractor with a Ford 720 loader and a Ford 723 backhoe. How do I check the hydraulic fluid on the loader. I know they share a common tank. On the cross bar in front of the drivers seat and across the top of the hood there is a fill / vent cap on a large pipe. If I look inside there is fluid inside. How high do I keep the fluid and what type do I use. Thanks, Frank