Set Node.js to $PATH
You don't have to worry about that, the apt-get install command will do that for you. It adds the path to the nodejs process (usually /usr/bin/node) to the global $PATH variable. This ensures that when you type node in your terminal it will start the nodejs process.
If for some weird reason you cannot start it, you'll have to manually add the path to your node installation to the $PATH. You can do this by editing your ~/.bashrc file and adding:
PATH=/usr/bin/node:$PATH
I've been trying to install npm and it has complained about node not being in the path. Funnily enough, nodejs was, but node wasn't. I ended up solving the problem thus:
$ cd /usr/bin/$ sudo ln -s nodejs node...which symlinks node to nodejs. Now npm installs without complaints.
Depending on which shell you are running, the answer may be different, but a good starting place might be http://www.troubleshooters.com/linux/prepostpath.htm