I suggest the first place you start is with the documentation, first Help -> Analysis, and then Help -> NX Nastran. There are two relevant documents at Help -> NX Nastran: Basic Nonlinear Analysis Users Guide and the Handbook of Nonlinear Analysis. Your question is too broad to provide any specific help. If you are new to Femap, have you done the example problems in Help -> Examples?. There are four there that involve SOL106: starting from Large deformation - Cantilever Beam. These problems are very simple, but they help with the Femap analysis setup for SOL106 non-linear. The most common point of non-linear analysis is that the "structure" stiffness changes under load. This may be because of material yield or nonlinear elasticity etc; or it may be due to contact/separation, or it may be due to general large deflection effects (eg. membrane stiffening of thin sheet) and/or the reorientation of load as the structure deflects. You need to do some reading and some example/test models.