He only needs to copy and paste… but make sure that you use the correct URL.
I use the URL I see in the address bar. CodePen has a share button that allows you to share that codepen with someone using a particular theme… on the top corner, at the right, you have some code that you can copy and paste too…
Don’t use the share facilities… not necessary and if you do, you’ll get a text with a link, not a view of the code and its result. At least, in Dicourse.
So I would say the right way is… load the window in your browser, copy the URL in the address bar… paste it in your post
The other thing to note is that the Pen won’t embed if it’s created anonymously. You have to have an account at CodePen (which is completely free, BTW).