Having trouble to find the node in ubuntu 14.04 after installing

I installed the NodeJS in Ubuntu 14.04 by nvm by following this site Installing NodeJS Though I had the following problem as

nvm ls
    sbin
mkdir: cannot create directory ‘/usr/sbin/alias’: Permission denied

Then I found to resolve this as (from NVM solution)

$ export NVM_DIR=~/.nvm
$ echo $NVM_DIR
/home/roy/.nvm

Then It works fine.

Now the problem, I face is that if I restart or even open a new console, I can't find the node again.

roy@Croy:~$ node -version
The program 'node' can be found in the following packages:

 * node

 * nodejs-legacy

Try: sudo apt-get install <selected package>

I have to follow those steps,

I do nvm install 0.11.13 then it shows

v0.11.13 is already installed.
Now using node v0.11.13

How to come out from here ?