1) Click "+"in the menu bar (Figure ①)-> Expression-> Symbolic expression (Figure ②)/QQ expression-> Choose one or more expressions you like. Next, press and hold the input box until you copy the options. Select the emoji you need and copy it. (as shown in the figure below)

2) Enter WeChat Settings-> Personal information-> Name. (as shown in the figure below)

3) Press and hold the input box until the paste option pops up, click Paste to save and return to the previous interface. You will see an emoticon added to the name. (as shown in the figure below)

The last thing I need to tell you is that color expressions are not supported. Can be displayed as characters. Only emoji expressions can be added, and no other expressions can be added.

Note: As shown below, the color expression in the red box is not available.