Following step you need to follow to install Node in your system
Step 1 : Refresh your local apt packages
To get the latest version of node js first refresh your local apt package manager. Use below command to do
sudo apt update
Step 2 : Install Node js from repository
Then directly install node js from the repository. Use below command to install
sudo apt install nodejs
Step 3 : Install npm, most of the cases you need to install this. So recommended is install npm while you install node.
If you want to use full feature with node package manager(npm) and also npm is very usefull and you need to install this to work freely. Basically npm will allow to further install node modules and packages in your application. Install npm using below command
sudo apt install nodejs
Step 4 : Installation finish and verify installation.
So if you did all the above things node is installed in your system. So to check that use
node -v to see node installation version and to see npm installation you can use npm -v to see installed version of npm
If you can see both version it is installed in your system and ready to work.