The black and the red go to the hot sides of the two duplex receptacles, respectively, i.e., the black to one duplex receptacle and the red to the other. The white goes to the neutral side of both receptacles. This can be done by connecting the white to one receptacle and then using a short piece of white wire connect the neutral sides of the two receptacles. Alternatively, you could use two short (6" or 7") pieces of white wire connected to the white neutral and send one to each duplex receptacle.
The above is assuming you want two separate duplex receptcles. This would be four receptacles total in a 2-gang box.
But if all you want is two receptacles (instead of two duplex receptacles for four total), then you could keep the octagonal box and put one duplex receptacle in it. You could wire it so each receptacle was controlled by a separate switch by breaking away the connecting link on the hot side (only).
By(By breaking away this tab you do disconnect the hot sides of two receptacles, but you could reconnect them later for use in a different arrangement if you want to. YuYou would connect the hot sides of the two receptacles of the duplex with a short piece of (black or red) insulated wire to reconnect them.)
This is assuming that there is a way to mount one duplex receptacle in an octagonal box and there is a proper cover plate for that mounting. For a 4" octagonoctagonal box there is a cover available that works. The duplex receptacle is attached to this cover plate and the cover plate attached to the octagonal box. This might look more industrial as opposed to finished residental, but it would save the trouble of replacing the octagonal ceiling box.