This is old, click here for the slightly improved one

gamejolt api
custom reporters (optional if you want the game to be easily able to detect if a trophy is unlocked or not)

first off go to the game page, gear icon thing at the top, game api then api settings

the private key is there but DO NOT SHARE IT WITH ANYONE, ESPECIALLY THE PUBLIC. so just hit show key, then follow this example just replacing the variables with the actual id and key

now you have to make login screen (you probably may have already created the message for that)

an example one

now that you made the login screen + logged into your account in the project, you wont be logged out of your account next time you smash the green flag. but it only logs you out by itself when you close the packaged version of [your game here].

ok its focus-on-trophies time. using my game PASTA for screenshots. (the trophies may not make it to the game, or will they?)

k now go here in your game's settings (if you dont have a game on here, simply go to gamejolt's usual page you start on, look for something that says "manage games", hit the plus then do some stuff)

if you scroll down and look at all types of trophies you can have in your game, you might say its similar to playstation (it kinda is)

so add a bronze trophy and it should be simple :)

now you will see an id on the trophy item of the list. that will be VERY important if you want the player to be able to get it.

ok now let me introduce you to these blocks (you might already know what the first two do)

and yes the first one is hyper important for trophies.

so if you put this block on the bottom of the login script you should get the trophy for logging in (or being logged in if you are still logged in)

as some of you guys know (if you ever touched a playstation 3 or later) the most common trophy is "All done" (the trophy's name from stray) on platinum and you get it for collecting every other trophy. i think you can do that on here as well

-=BONUS PART=-
to easily detect if the trophy (fetched using its id) is unlocked or not you need the "Custom Reporters" extension and that is simpler than the simplest full game ever

all you need to code, it takes only one smol script lol

and yeah there you go