Open Portal Solution

1. why i reg new user but i can't to login dat using dat user id except using admin id...

maybe the database is not complete when you install it, or the config.php is wrong when you change it.

2. totally i donno how to use phpnuke even it alredy running!!! i meanz dat how to edit and want my website appears on dat pages... where should i edit...should i edit it in content page on admin.?

In phpnuke you can edit two thing, firstly in terms of front page or the themes and secondly, the content.
The content you can done it at the front page or front end. for the front page or themes you can change the appearance only with the knowledge of coding, and know what files you can change.

3. can u explain to me the purpose of administration menu and module administration-->the important one only..HOW TO USE?

Admin page is for you to manage the appearance of the front page, the module is to make an easier managing and also to add feature that you want it.
For me all the feature in admin is important, you have to learn and know all the things in admin.