Hydraulic Oil Drain Plug
The drain plug is at the bottom of the top link casting, circled in green.
The filler/dipstick is on top of the tank under the seat towards the back. Some are combined filler dipsticks, some are separate, some do not have a dipstick.
If you do not have a dipstick the oil needs to be about an inch below the top of the tank. On the top of the tank under the seat, towards the front is a triangular plate which when removed gives better access into the tank to check the oil level.
The oil must be ISO 32, this is critical, anything else such as universal oil will cause the hydraulics to become sluggish.