This package provide the following commands:
helm-org-agenda-files-headings
Allows searching in headings of all your org files.
helm-org-in-buffer-headings
Allows searching in headings of current org buffer.
helm-org-parent-headings
Find the parents heading of current heading.
helm-org-capture-templates
Completion on org capture templates.
It also make org-capture and org-set-tags working properly with
helm-mode when adding helm-org-completing-read-tags to
helm-completing-read-handlers-alist.
The easiest way is to install from Melpa with
M-x helm-list-elisp-packages if helm is already installed or with M-x
package-install => helm-org.
To install from source, ensure Helm is installed (see
https://github.com/emacs-helm/helm/wiki#install for this) then install
helm-org.el in your load-path, byte-compile it, and add
(require 'helm-org) to your init file.
Once you start M-x helm-org-in-buffer-headings or M-x helm-org-agenda-files-headings
hit C-h c to customize helm-org.
To make org-capture and org-set-tags working properly with Helm,
add them to helm-completing-read-handlers-alist:
(add-to-list 'helm-completing-read-handlers-alist '(org-capture . helm-org-completing-read-tags))
(add-to-list 'helm-completing-read-handlers-alist '(org-set-tags . helm-org-completing-read-tags))
Of course you can also use the customize interface to setup helm-completing-read-handlers-alist.