I submitted a news item about an updated patch, but it was rejected because "The updated patch must be available here first before submitting a News."
So, how does the patch become available here?
You can not submit the news if the update was not yet submitted/accepted to the site. Use the "edit entry" and wait until it is accepted. Then submit news.
What should I put for "filename"? Just the address for the file on the remote site?
As it is says on the right "URL only", which basically means you need to upload the IPS or other patch to the Scratchpad on this site first. When the file is uploaded, you can link to it. Add this link in the filename field. The same with the readme as well as screenshots (they are also "Url only"). The other popular uploading site is zebucket (http://www.bwass.org/bucket/
) or Dropbox. Do not upload or link to megaupload, and similar. The link must be a direct download.