Mine do well in part sun.
I'd suggest the sow them in the spring, or winter sow them in containers.

I'm sure they would do really well if they sowed them now; but it might be a little tricky distinguishing the seedlings from whatever weeds seeds germinate alongside them in the spring.

I'm scattering a few this fall and then late winter sowing them in March/April. Any earlier winter sowing caused rot for me this last spring. They are late germinators and demand warmer temps - at least this year.

I have four o'clocks growing all from just scattering in areas that I know I will not mistake as weeds in the fall. Every year they return by this method......and they smell so good by a window.... I am even trying some inside as house plants.....

Mine are in part shade and do great. It shouldn't be a problem to sow them now. The seedlings don't look like any weeds I know. Mine self seed every year and I never have a problem with weeding.

The half'n'half method gets my vote. Half now, half in spring. Doubles your chances of success.