Once you have purchased and downloaded the XenForo zip package, you will need to extract the zip and upload all the files from the contained upload directory onto your web server. You may upload into your web root, or any folder within the web root. This shall be referred to as your XenForo Directory.
Having uploaded the necessary files, you should direct your web browser to the URL that corresponds to your XenForo Directory and add '/install' to the address (eg: http://www.example.com/xenforo/install). This will trigger the installation process, which will guide you through the necessary steps to get a working XenForo installation running on your server.
Please note that the installation routine will direct you to ensure that the data and internal_data directories within your XenForo Directory are writeable by the webserver (ie: chmod 0777).
In your case the installation will be on your local hard drive.
You will need to start XAMPP and the Apache and MySQL services before you can access the local server.
I put the folder on my desktop top titled xenforo, which is essentially the "upload" file found in the package. I tried every possible combo to get me to the install file like http://localhost/local/xenforo/install/ and I get the object not found error