How to change ad size on wordpress?

[Skyhr]

Hi,

I'd like to start split-testing my ads, how do I, for example, change the leaderboard (728x90) to a large rectangle?

And how to I change the right side and main rectangles as well?

(i don't mean the actual ads I know how to do that, I mean the actual wordpress template. If I use med rect on leaderboard, the shape is still a leaderboard, etc)

[Skyhr]

In case anyone's wondering/reading this, the problem I had was that I somehow changed my publisher ID but didn't change my ad_slot so no ads were showing.

I changed the ads sizes/types/placements fine now. And I'd have to say I'm pretty pleased with the layout.