This is what the wikicode for the talk page looks like. You can add a reply by copying this code and adding it below the other comments:
::Hi! Can you give me any advice for improving this article?--~~~~
The two colon characters at the beginning will indent this message twice, so that it appears as a reply to the second comment. And the four tilde characters at the end will automatically be converted into a signature, with your username and the date and time you left the message.