Isolation pertains to how one relates psychologically with the exterior world, specifically in maintaining internal silence and saving one's energies, never wasting them through identification with external phenomena.
This does not mean one is antisocial or a "zombie," but that one learns to live life intensely with the consciousness, with comprehension, happiness, rectitude and love, for by saving one's psychological, emotional, vital and mechanical forces, the disciple in turn has energy by which to develop the consciousness to its full potential.
For understanding isolation or hermetic silence,
study this chapter!
For knowing suitable methods,
read the rest of this book!