For rate button it's just url_open( 'http://your.google.play.url.here' ) on mouse click event. Before that you should show a message asking the user to rate your game. One button should be "rate now" and other "cancel" (or "remind later"). If player taps on "rate now" button you open url of your game in Google Play store.
Hey sercan,
To show the leaderboards you can use the following code:
Code:
if achievement_available()
{
instance_create(0,0,obj_pause); //optional, if you have a pause object it is wise to use it while the player is looking at the leaderboards
achievement_show_leaderboards();
}
Remember that, in order for this to work, you must have the Google Services thingy enabled.