To create styles you have to actually play all the parts - and all the notes in the timing you want. There is no magic button that does it for you. Style creation from scratch on the keyboard is not simple or fast. It is typically a lot of work even for people who are knowledgeable. I would say less than 1% of arranger owners ever successfully create styles from scratch. If you want to get into style creation start by modifying existing styles, small modifications at first, to learn your way. You will get better and more adventurous with experience, but most find full style creation from scratch on the keyboard is a step much too difficult. The pros who make styles have tools you don’t have, lots of experience and sophisticated musical chops.
Mike