Standpipe drain for washing machine and iron curtain/H2O softener

[Kdogat]

I'm attaching some pics of my basement setup. Would like some tips on installing a standpipe drain(s).

 

[Terry]

I can't see on the picture how the small pipe ties into the larger cast iron pipe, but sometimes you have a 2" hub there where you can install a larger 2" pipe.
Regardless, you would wye off the horizontal there, and run similar to the sink waste, with a santee on the vertical, trap arm and p-trap, and then tie the vent back at 42" above the floor to the other vent.