How to transfer a purchased app from iPhone to iPad?
There are (at least) two ways to accomplish that

via iTunes


sync your iPhone with iTunes. This will copy Talking Ben to iTunes
connect your iPad to the same computer
click on the iPad name in in the sidebar and go to the the Apps section
check the mark in front of Talking Ben
sync the iPad -> Talking Ben gets copied to the iPad


directly on the iPad


open the App Store app
tap on Purchases (or just search for Talking Ben again)
install


The iPad option only works if you are logged into the App Store with the same Apple ID on both devices, the iTunes option also works with different IDs.



As pointed out in the comment certain applications provide a specific iPad version which must be bought separately. You can still install the iPhone version in the iPad as well but will have to accept the usual restrictions concerning screen size unless the app was specifically coded to work both on iPad and iPhone.