It will be better and more helpful if you clearly define the problem you wish to solve.

As mentioned, you need to clarify your problem more. however in general to solve any non linear problem in FEA you need to introduce the failure criteria of your sample/material tested "Points beyond elastic region" and feed it to ANSYS.

As mentioned above, you need to define the problem clearly. There are different sources of nonlinearity such as: material nonlinearity (when the stress-strain curve of the material is nonlinear or having plastic material property) , geometrical nonlinearity (large deflection as an example), and contact nonlinearity (such as friction between between two surfaces or metal forming process. So, a clear idea about the problem you are going to solve will be of a value.

Thanks for the response.