'Enabling' Steam Achievements

I tried to follow the instructions in the manual as well as the wiki for SMAPI and I just can't understand it. I feel like the wording just doesn't make sense for me.
I use Steam and properties for Stardew Valley don't have an option to change the launch options.

I also don't use Multiplayer so I'm not sure what I would put in, also not sure what I need to change... I guess this should be self explanatory, but I dunno how changing the steam path itself will add the achievements? It seems like that's what it wants me to do. I use other games on steam, not just Stardew... Yes I'm an idiot, and yes I'm completely confused.