I have a 1994 Fleetwood Coronado with HWH levelling jacks and the reservoir is located on the passenger side above and forward of the front wheel well. The reservoir is about a 7" diameter horizontal cylinder with a filler cap mounted on top. Check HWH website for the recommended type of hydraulic fluid. I seem to recall I had used an automatic transmission fluid (red in colour).
Word of Caution, make sure your levelling jacks are retracted in the normal storage position when adding the hydraulic fluid. My levelling jacks were down when I checked the fluid level, so it appeared the fluid level was low (because the fluid flows down to the extended jacks) and I topped-up the fluid to the full mark. However when I started my motorhome and retracted the jacks, all the excess fluid spurted out of the filler cap onto the underside of the motorhome and all over my driveway!
It was a difficult job to remove the red oily residue from the concrete driveway. Luckily I had a large bag of absorbent material to soak up the oil and shovel it into plastic garbage bags, and then used an engine degreaser to remove the remaining oil residue.
I hope this will be of some help to you, Good Luck!