BannersABC.com, Addesigner.com, mybannermaker.com, etc. (Google for more). There are a number of different online banner-builders. Spend a few minutes comparing the various features, and pick the one that suits you best. Follow the on-screen prompts and methods to build your banner. They will often have their own artwork that you can use, or you can import images of your own creation to add to the banner. When finished, there will generally be an export function that will let you specify which folder or directory you want to save to, and file format (jpeg is usually good). Follow the instructions, save, download, and use as needed.

TL;DR in Chinese:
请先登录以下网站：BannersABC.com、Addesigner.com及mybannermaker.com等等（谷歌上可以搜到更多）。 添加文本及图片。 生成横幅。