Following the same steps as Dipak C in his question regarding void-variable helm-map error but still cannot solve the problem even after adding
(package-initialize) just after
(require 'helm-config) as I understand from the solution.
package-initialize after loading helm won't make a difference, doing it before loading helm might. Also see https://github.com/emacs-helm/helm#install-from-emacs-packaging-system and https://github.com/emacs-helm/helm/wiki#faq.