If you mean on a homescreen, press and hold and you'll get the option to move the icon. Then you can arrange as you like.
If you mean in the app drawer, every launcher I've used orders them alphabetically by default. Some have options though - if there's a menu button visible in the app drawer (3 dots, probably in a top corner if it's there) use that and see whether there are any sorting options. It may be that they are being sorted by install data or when last used.