Where you enter the text of your credits has a specific format. The top is one solid box, while all of the lower text entry points are in two different columns. There is no absolute for how credits are supposed to roll, but, since you only get a solid single box at the top, you may want to begin with the cast.
The reason for this is you can list Cast at the very top, and then just list each actor afterward. This lets people know that the positions that you are listing here are part of the cast and not crew positions. Here you can list their names on the right and their characters on the left. You can also just try listing the cast names without their characters. If you do this, you should just put their names in the right-hand column.