No offence, but you really need to do a search and possibly a lot of reading about phpnuke, postnuke, XOOPS, Mambo, and possibly blog software such as Wordpress.

You need to figure out what you want to acheive with your website, what its focus will be, what features you need, will you need a discussion board and if so, can it be seperate or does it have to be integrated into your Content Management System as a module?

In other words, you need to really think about what you want for yourself and for your guests/members.

No amount of talking you through the finer points of phpnuke will help you until you do the above.

BTW, the file you refer to is simpy one type of compression which means you will also need some type of file decompression utility such as WinZIP, or StuffIt.