Character/Object-creation system (Mesh-recombining-system)

Hello there.
Could anybody please give me a hint or starting point, to how I could combine different meshs I importet into one object?
An example would be:
different parts of a body (arms,legs,torso,head,etc…) combined make one charackter,
or
the different parts of a spaceship combined make a “new” space ship (Kinetic Void)
And after that, how I would be able do make this work like a Charackter-Creator.

Thank you