Your frame should have come with the required nylon cups. OSBB is similar to pressfit where the BB30 bearings press into cups which press into the frame.
The cups do have a "lip" to them to space the BB to the required BB30 width.
If you bought the frame from the shop you are dealing with they owe you a set of cups for the OSBB. Once you have those cups everything installs as normal for a BB30 crankset.
As you can see from my post made about installing my Zipp crankset thew nylon cups have a lip to space the bb to the correct width.
Still waiting on a few more parts but I have the cranks installed!
The Zipp distributor in Canada didn't bring in the BB30 adapters so I made my own as seen here.