1) open cmd
2) cd '/path-to-core-folder'
3) install node if you don't have
4) fire npm install gulp -g
5) fire npm init 
6) fire npm install (It will adds dependancies in node_module folder)
5) open gulpfile.js (if you want to change version of files,update version variable)
6) fire gulp (if you want to minify specific module then use gulp 'module-name' eg. BookingModule)
7) then update relevants path in js.shtml file