"A platform already exists" error message

Hi,

I'm following some instructions from a tutorial and have just tried to create the app for Android using ionic (using the command ionic platform add android but I get the following message:

!!----------------------------------------------------------------------!!
!!  Run/restart gulp to configure the custom Android application class  !!
!!----------------------------------------------------------------------!!
Saving platform to package.json file
A platform already exists - now updating the entry: android android

It seems to have created a package.json file and populated it with some of the relevant data so I'm not sure what I've done wrong. I can't actually see the app in the folder though.

Any ideas please? Many thanks