@koko how are you trying to?
these are the exact steps [mentioned on appium.io]
brew install node # get node.js
npm install -g appium # get appium
npm install wd # get appium client
appium & # start appium
node your-appium-test.js
So if you already have node then no need to uninstall just go ahead with ‘npm install -g appium’
and if some package not found then just do ‘npm update’