How to open the doc file for a vim plugin?

I just downloaded the Rails vim plugin from here.

One of the file that it contain is a doc file that will be extracted to ~/.vim/doc/rails.txt

How do I open the content of this help file in vim ?

I tried :help rails to no avail.

Solution 1:

After installing a new help file into ~/.vim/doc, you need to rebuild the help tags file:

:helptags ~/.vim/doc

Then your :help rails command should work.

garyjohn's answer is right, but I just want to mention that pathogen provides an easy way to run helptags for each plugin (note the case):

:Helptags