The %command% method usually works, if you got the game through Steam. Basically, right click on the game in Steam, go to Properties, and go to "Set Launch Options". Input this - "(add the location of Stardew Valley)\StardewModdingAPI.exe" %command% , then apply. As an example, mine looks something like this: "C:\Games\Steam\steamapps\common\Stardew Valley\StardewModdingAPI.exe" %command% If I wasn't clear enough, there should be instructions a bit further down in this thread, if I remember right. http://community.playstarbound.com/threads/how-to-boot-the-game-in-steam-with-smapi.108280/ Edit - Just in case I misinterpreted... When using SMAPI, your achievements WILL show up in the game itself, but NOT in Steam (unless it's been fixed, which I don't know...). Hence the method mentioned above. Sorry if I got it wrong again, I'm running on very little sleep atm...
If using this method, 95% of the time, achievements should show up on Steam too, sometimes it bugs out though and refuses to, which is where I usually restart the day and try again.