The pattern is really basic and the top is pulled shut at the end. So you won't need to do any decreasing. It's more like a tube-shaped structure. It's done as a flat panel and sewn with a seam line. The top is sewn like a fold for a pleasing look to the eye. Roll the bottom edge for the depth of the hat.
This is the Knit Preemie Hat for Beginners.
We have another hat pattern that has a tutorial for both the of the hats shown in the picture below. There are several sizes to try.
If knitting isn't your cup of tea. We have a crochet beginner hat pattern below too.
We also have this pattern that is more basic and quick for building charity boxes too.