Whether it is Android, Symbian or IOS, it is actually very simple to add a cartoon pattern:

The first step is to open WeChat and find someone to chat with, and then select to add an expression in the input box. Then select Emoji expressions (other expressions cannot be added) and select one or more at will.

Now that the text box already has the expression you selected, press and hold the text box to select copy all or select the expression you want to copy.

The next step is to open the settings of WeChat and paste it wherever you want to add the emoticon [when pasting, "mouth" will usually be displayed, don't worry about it and save it]!