Call script from custom class - v8.0.1

Hello Experts

I have a custom class, and in the new operator I am calling an existing script to do some calculations. However, when I compile I get the following error:

Reference to a non-shared member requires an object reference

I guess this make sense since all the customer scripts reside in a separate class.

Question is: How can I access the functions (i.e. scripts) from within my custom class?

Thanks

Kin