If you mean code as in macros, then select the macro (or actions) you wish to share, then click the Share icon in the toolbar and select Keyboard Maestro forum.
If you mean code as in lines of code, you can wrap blocks using three single quotes on a blank line, then paste (text) your code, then three more single quotes on a blank line to end the block.
Also, @_jims wrote a great post showing many of the forum tools you can use to make your posts easier to read.
-rob.