They say to install your outboard bb to this first before pressing the assembly into your PF30 bottom bracket. To do this, you need a flat-face vice to hold the adapter (on the flats) while you screw in the cup.
I found that once you press in the adapter to your frame, it's pretty solid, so you can actually press in the adapter first and then just screw in your outboard bb like you would normally do. Much easier. YMMV.
BTW, this adds 37g to your build assuming you get rid of your original plastic sleeve for your outboard bearings.