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the module version of phpadsnew really isn't any different from the stand alone, other than it is now a module.
it doesn't interact with XOOPS any more than that.
you will have to read the huge manual that goes along with phpadsnew to get an understanding. i'm afraid it's way out of the scope of a forum explaination.
But to answer your question, when you finally get an ad ready, you will create what is called invocation code. you can place this code anywhere in an html file. for instance, you can place it in your theme template file. or you can paste the code into blocks and display it that way.
one thing to note though, if you place the code into your theme template file, you may have to edit the php end tags because the smarty handling might alter the code a bit.