Icons are signs that are used to give hints and suggestion to users when determining which operation to trigger. It is a important auxiliary to text prompt. In graphical systems, icons are often designed to be a square of pixels ranging from 16*16 to 256*256. Some systems use scalable vector icons, or even larger icons of 512*512.
This entry gives brief introduction to installation of icon theme in deepin desktop environment.
Download the deb package of the icon theme you preferred, install it, then step to Control center -> Personalization -> Theme, and choose the installed icon theme.
If you get a compressed file for the icon theme, first decompress it, then copy the extracted file to directory /usr/share/icons (you may need root permission to do so). Now you should be able to find it in the theme list of Control Center.