Select Mobile Apps.
Select the desired mobile app.
Under Push Access Type, select iOS and click Configure.
You will need a Certificate and Password from your mobile apps developer. The developer receives these by logging into the Apple Developer Member Center, setting up and downloading a push notification certificate for your app, and exporting the content. The developer sets the password when making the export. IMPORTANT: The certificate should be appropriate for the kind of environment you’re using — Sandbox or Production. Verify this with your Marketo Admin or mobile apps developer.
Select your Certificate, enter your Password, and click Save.
Great Job! Make sure you also configure the app with Android.