Download and run the install script using curl:
curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.30.1/install.sh | bash
or use wget:
wget -qO- https://raw.githubusercontent.com/creationix/nvm/v0.30.1/install.sh | bash
nvm install 4.2.3
where 4.2.3 is the version you want to use.
nvm use 4.2.3
Check out the official github page for NVM for details NVM