Once you are logged in to PokerDIY it is very simple to reply to any Poker Game ad you find. There are 2 ways to contact someone when you are viewing the Poker Game detail page - the first is via Private Message and the second is via a profile Wall post.
To send a Private Message you can can click on the "Send Message" button. This will take you to your message center and you can send the ad creator a message that only he/she will see.
Alternatively you can click on the ad creator's name to view their profile. You can now write a message on their profile Wall but bear in mind all the people who can see their Wall will see this message.
You will notice in both these cases that you don't need to know their email address and they don't need to know yours - this is the beauty of PokerDIY - it takes out the danger of contacting strangers by acting as the middle-man. Likewise, if you list a Poker Game ad you should not put your contact details in. Interested parties can contact you in one of the methods described above.