How can I make a banner?

Before bạn ask:
• I'm not new, I've been here since February.
• I already googled it and shit but I've found nothing.
• I know I can use Paint but I wanna use something better. I want to make a detailed banner, not a basic, simple one.
• I've read most of the các bài viết on each club on here, but none of them can help me.
• I already know which programs to use. I also know I can use websites for free..I just don't like how they turn out.

I downloaded this software for free called PhotoScape. I've heard people say they make banners with it. I've tried but I don't know how. Can anyone help me?