I cant change the brush type

Hi i just downloaded Aseprite and im watching a tutorial but I cant change brush type
Whatever I pick it looks like this and its a square

hi, there!
the size of the brush is 1 pixel, so it will always be square.

This is because you are using brush size of 1 pixel. 1 pixel can’t be any shape other than 1 pixel (which is usually a square but could also be other kinds of rectangles on certain displays, but that’s kinda beside the point Pixel aspect ratio - Wikipedia). To use other brush shapes you would have to use a larger brush, because when you’re drawing with 1 pixel, either you fill in that pixel or not, you can’t partially fill in a pixel with a circle because it’s the smallest possible measurement in an image.