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 receptcle 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 breakeing away this tab you do permanently disconnect the hot sides of two receptacles. You could use a short piece of black 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" octagon box there is a cover available that works.