When designing a UI, you should consider the overall color scheme, the shape and color of each icon, and the tone of the website to be expressed (lively and serious). According to these colors, you should consider the placement of each pixel. If you think what I said is interesting, you can have a try. Then you should be prepared for the following:
Learn Adobe design software, especially Photoshop and illustrator, learn color matching, composition, light and shadow, etc.
After learning, you can look back and see if you are suitable.