You said it had a manual transmission. A manual transmission has a clutch pedal. Now you say it doesn't have a clutch pedal.
So, if your C500 YS-80 doesn't have a clutch pedal, then it has a Hydratork powershift transmission, which is not a full automatic, unlike an auto.
It should have 2 column-mounted levers, one is Forward-Reverse lever, the other is a Hi and Lo Speed lever. You manually select the desired direction and speed selection, and you can do this without any need for a foot-operated clutch. Clark advise to not change speeds or direction whilst moving.
There are two brake-type pedals, the left one is the inching pedal, and the right one is the service brake pedal. Depressing the left inching pedal approximately 1-1/2 inches reduces oil pressure to the transmission clutch packs, effectively disengaging the transmission so you can rev the engine for faster hydraulic speeds. Pressing down further on the inching pedal applies the brakes. The right pedal actuates the brakes only.
The Hydratork transmission uses Dexron Automatic transmission fluid. Clark originally specified Type A, Suffix A type transmission fluid, but this oil specification became obsolete in 1967, and was replaced by Dexron.
The transmission oil level should be checked with warm oil and the engine running.