Hi, The dipstick tube is located at the rear of the engine - it will have a black plastic cap & should have a black or red locking pin that is broken off to remove the cap.
The oil level needs to be checked with a workshop dipstick - you should be able to but these from tool suppliers or are available on ebay
Here is a link to one on ebay: transmission dipstick
The oil is added through this dipstick tube with a small funnel
The dipstick is required to ensure the oil level is correct
Best regards, Paul