Start with a Free Body Diagram to understand loading conditions.
Often forces are only expected/applied on a small section of a model's surface. CAD software allows you to 'break' the surface into multiple parts, then apply constraints or forces ONLY there.
NX command is Insert -> trim -> divide face
Solidworks command is Insert -> split line
Thorough FEA analysis should include regular expected use, worst case use, and expected misuse cases.
This is especially true for consumer products and applications to avoid injury and lawsuits.