Hello and welcome, about the things you ask:
The X-Change Credits you earn by viewing other users' ads/links, allow your to advertise your site or link, to use them you do as follow:
1) Go to your account pageand Click Manage Ads
2) In the Drop Down Box choose Exchange Site and press Manage
3) Press Add New Site
4) Put the title you want in Title and Put the link you want in:
Target Url (h**p://www.mysite.com
5) Check the "Does Not Violate Terms" (Read the Terms and check your site first) and Press "Add LInk"
Then Add the credits you want, and it will start showing to other members.
About tickets, grom your account click "COntests" and you can read all about tickets and other contests