There is no "dashboard" as such. If there is a file /wp/index.php, you can simply enter the URL
http://www.mydomain.com/wp into your browser and you should be running Wordpress. If you don't want to have to always enter the /wp part, you can do a URL rewrite in /.htaccess:
RewriteEngine On
RewriteCond %{REQUEST_URI} !^/wp [NC]
RewriteRule ^(.*)$ /wp/$1 [L]
With that, a visitor to
http://www.mydomain.com will find themselves magically in /wp.
If your server is still running PHP 4 by default (I'm surprised that any at LP still are), there should be a button in the control panel (LPCP or cPanel) to switch to PHP 5. If you're not sure what version is running, run this little PHP script:
<?php phpinfo(); ?>
It will tell you for sure what PHP version you're running (among many other things). If you still can't get it to show PHP 5, open a support ticket (
support@lunarpages.com). As I think that all servers are supposed to be at PHP 5.3 now, maybe you should let them know that they overlooked one? Make sure that your /.htaccess doesn't have an entry in it reverting to PHP 4.