Hi,
When I am running a mobile install campaign where do I link my landing page to the Andorid Play or do I link it to the install button in the play store ?
I'd say that unless you wanna send installs for free, link to your affiliate link that you get from your cpa network 
I was thinking that I must click on the download link in the App Store and then link it to my landing page
No mate, on your landing page you link to the affiliate tracking link that you get from the cpa network.