Best way to vent new shower.

[SpencerV]

I'm adding a shower to my bathroom and I would like to get some advice on how to tie into the drain and vent.

There is also a 3 inch line below the shower that leads to a vent and then a toilet. If I connect to that line does it count as vented?

 

[Terry]

It looks like you might have a washer there. Those can't wet vent a shower.
I would plan on adding a vent for the shower.

A shower vent run in 2" will vent a toilet, but a toilet can't vent a shower.