Hi Filipe
Locate the file 'httpd.conf' which can befound within c:\program files\apache group\apache\conf (assuming that you are using windows). Open the httpd.conf file in notepad and search for 'DirectoryIndex'. Apache launches 'index.html' by default, you will find this a couple of lines down which you can then manually edit.
Also run a search for 'DocumentRoot'. Apache default is c:\program files\apache group\apache\htdocs. Once again, you can edit this path to suit you.
Save the changes you have made and then restart the apache web server. Hope this answers your question.
-Abi