Ok here we go again with my ignorance of technology!Is it a...

Ok here we go again with my ignorance of technology!
Is it a computer app or only a mobile phone app?
I downloaded the app on my computer but can not work out how to open it on my computer to use it. It sais that I have installed it but what next?
Any help with the steps to take so I can use it on my computer would be appreciated.
Cant use it on my mobile as I don't know how to use a keyboard on a mobile phone.