Story Advice

I have yet to write a story on Mibba. I was wondering if anyone had any advice on how to start out the a story. Do I write down the general idea of the plot first? Do I develop my characters before I begin to write? I need help. If anyone has any input to give me. Or sites that will help me get started. All help would be greatly appreciated by all. I have another question. How do you make a banner? And how do you change the layout of your profile? I know they have explanations on here but I don't understand what it means.