I did as how moplin mentioned .But in my case service send the JWT in response headers ,as a value under the key "Authorization".
Authorization ?Bearer eyJhbGciOiJIUzUxMiJ9.eyJzdWIiOiJpbWFsIiwiZXhwIjoxNDk4OTIwOTEyfQ.dYEbf4x5TGr_kTtwywKPI2S-xYhsp5RIIBdOa_wl9soqaFkUUKfy73kaMAv_c-6cxTAqBwtskOfr-Gm3QI0gpQ
What I did was ,make a Global variable in postman as
key->jwt
value->blahblah
in login request->Tests Tab, add
postman.clearGlobalVariable("jwt");
postman.setGlobalVariable("jwt", postman.getResponseHeader("Authorization"));
in other requests select the Headers tab and give
key->Authorization
value->{{jwt}}