Attempt to download app, says it's already installed on my Iphone4 I had the sirusxm app on my phone and everytime it would give me problems I would delete it and reinstall it.  I forgot that I had just recently changed my email password from my laptop, which is synced with my phone.  When I went to download the app after having once again delete it due to having problems, the column which you click on to download quickly changes to purchased.  The app is not on my phone.  How can I get it?
There is a difference between an app that has been purchased and one that is installed. To install a purchased app, open the App Store app on your iOS device.

Click on the Updates button in the lower right corner to advance to the Updates pane:



Click in the Purchased area near the top of the screen to advance to the Purchased pane:



Select the Not on this iDevice tab to see purchased apps that aren't currently installed:



Select the app you're looking for from the list and install it.