Click on the black buttons to change stuff. Click on the cat's eyes to change their style. Click on the background to change its color. The light grey button is for making 'it' lighter and the dark grey button is for making 'it' darker. Next to 'extra features' you can click on the grey button with the pencil to change the color. If you want, you can take a screenshot of the cat you created and make it your thumbnail!
This is one of my first scratch projects... 4 years later I'm not sure what to make of it.