Once the files are finished uploading, you must set permissions (or CHMOD) several places. This is necessary to ensure that XenForo can write to those parts of your server. You can usually do this with your FTP client. In the set of files and directories you just uploaded, you will see 2 folders: data and internal_data. These two directories must be set to world writeable (CHMOD 0777) or give the IUSR_ Full Control in Windows. Keep your FTP client open; you may still need it for the next step.
I am needing to find out what file permissions i need to have for what. The text I provided is not concrete enough, I am not able to upload attachments or photos in the gallery.