Nanopolymer is different nanocomposite is different;
for nano polymers any one of the dimensions of the polymer should be in nano size, may be diameter ( then nano fibers) or thichness (nanosheets, nanofilms) etc. One of the convinient way to prepare nanofibers is electrospinning
first of all, you need to study some nano-related books to be familiar with the nano terms and definitions.
Polymeric nanocomposites may be produced through a wide range of methods( e.g. incorporation of nanoparticles into the polymeric matrices, in situ synthesis of nanoparticles in a polymeric matrix, ...)
The method depends on your polymer, the nanoparticles, the processing condition and equipment, the application, and the properties you are looking for.