The first line might have five syllables. The second line has seven syllables, and the third line has five syllables. If trying to write haiku for the first time, it's important to clear your mind of any nagging thoughts. Take a long walk and observe your surroundings. What strikes your fancy could be the basis for your haiku.
Free association is another way to come up with ideas.
Make a list of random thoughts one after another and see if there is any linking characteristics. Focus on a single image chosen from your list. You want to avoid telling a story, however, you do want to create an image that is sharp, like a photograph. Read examples of haiku. This icy night.