Where and how do you put transmission fluid in a 2006 Freightliner Century with a Eaton Fuller manual transmission

Most manual transmissions don't use transmission fluid such as you would find in Automatic Transmissions... that I have ever heard of. They use a heavy grade multi-viscosity oil called, "gear oil}, especially made for manual transmissions. Typically, it's 70-90W SAE NGLI 4 or 5 grade oil pr maybe 90-110W SAE depending upon the mfr. To be sure, look at your owner's manual or use a Fleet Services catalog under one of big oil mfrs, like Shell, Ashland's Valvoline, Mobil, Quarter State, or Texaco. Usually, there is a large bolt at the sump, don't remove and drain out the fluid until you locate the fill access nut and can loosen it. Make sure your truck is on level ground. The fill access bolt is usually either a quarter inch square nut that you can turn with a 1/4" open-end wrench; however, some use an indented 1/4" or 1/2" indented square bolt/plug that you can use a suitably sized ratchet extension bar end with a ratchet to open. (Shorter length bar is often better for work in close quarters.) You will find the fill plug on one the side of the transmission casing, up high when your lying on your back underneath. Open the fill plug first, before you drain the transmission sump. Many transmission sump drain bolts have a thin metal washer on them that serve as a gasket... get a new one to replace the old one. Using the old one may cause a slow leak you won't be able to stop the very slow dripping on. The sump nut will have small pieces of metal filings on it, collected as the transmission gears wear... wipe off the magnetic underside of the bolt to clean it out with a rag. A toothpick works great at getting the fine metal particles off from around the edges. (Reminder: Take the fill port bolt off first and then drain the transmission sump by removing the sump nut.) After draining, put the "cleaned" sump bolt back on with the new washer. Ensure you have a short length of clear plastic tubing with you to push onto the open nozzle end of the gear oil container that is best cut with a carpet or box cutting razor with handle. (Remember to break the inner seal underneath the screw top nozzle.) (TIP: If there is little room to raise the bottle above the fill hole and squeeze it to empty it through the plastic tube into the fill port on the transmission, buy an extra quart of gear oil... it is easier to squeeze a full bottle and and top it up with another one as it gets too hard to squeeze when empty to make the oil come out..; go slow or you can squeeze so hard the nozzle will break and cover your hand with gear oil.) Fill the Manual Transmission case to the point where gear oil starts to trickle out of the fill hole and then put the square bolt back in with the open-end wrench or ratchet extension bar end. (TIP: Using an extension bar end is preferable to just a ratchet tip as it adds leverage to make the removal easier.)