Help! Boardman BB33 (PF30) change. Is this normal!

pbassred

Hi, I'm changing my Boardman CXteam's crank to a shimano (24mm) from a PF30. I have a Rotor 4624 bottom bracket. However its diameter is constant whereas the frame has a step in it so I can't press the bearing in. Is anyone familiar with the Boardman or have insight?
(edit - typo in title should read "BB30" NOT "33". There is no way to change it.)