Tuning current limitation for VCSEL laserdiode
How do I limit the current based on the pin diagram?

You don't. You use the features of the circuit that is supplying the pin to limit the current.
For example, you use a benchtop supply with a current limit function.
The instruction is probably meant only to describe benchtop testing, where it's easy to make a mistake in the connection polarity, etc. For your final circuit you might not need this limiting capability (but it would be a good idea to confirm this with the vendor).