How you delete an app from itune (not the ipad)

I have problems with an app that refuse to install how I delete it from itune?

I'm using Mac, select the app icon in the list and then Delete key nor Supp Key nor Command Delete worked.

Bad job Apple where is hidden this famous ability of designing a good ergonomic???

 

Ha ok thanks I was trying do it at the wrong place, but it's very new this new Apps section. Ha well ok.

And now I have fully delete it, I understood I can buy it again through itunes and won't pay a second time, that's right?

 

Thanks I wasn't sure.