htaccess wordpress=mod rewrite

To be honest im a newbie with htaccess. I have some problems with it – especially with mod rewrite but lets start from the begining. my public_html looks like that:
+wp
+images
index.html
404.html
…
main.html
.htaccess

and of course the wp directory is the one with WP. I want to have a start page with different name than index – in my case it is main.html so i added a line to htaccess:
DirectoryIndex main.html
And it should works but.. I have a menu bar in this file(main.html) with links to pages in my wordpress so they looks like that:
wp/index.php
wp/index.php?id=4
…
and in theory it should works.but only in theory. When you will click on that link nothing will change. URL in web browser will change for example: mydomain.com/?id=4 but this is only thing which is changing – the url in browser but pages dont appear. so i think there is a problem with connection with my index.php file in wp directory. the worst thing is that with this htaccess with directoryindex main.html don’t work wp-admin and there are problems with images. So how to fix this problem how to write correct htaccess? The most important thing to me is redirection of url. I dont want to move wordpress from wp dir to root – i want to have that when you will type in browser http://www.mydomain.com url only with files like index etc. I dont want to see http://www.mydomain.com/wp/… how to do it;/?