Rename procedures:
1) right click on your rar file
2) select "rename"
3) replace the file extension from .rar to .torrent
4) upload this torrent file in your reply post
5) done
if you cannot see the extension of your file, then
1) open the explorer
2) choose "tools"
3) click "options"
4) click the tab "view"
5) click on item#12 "hidden the extension of shown files" and
remove the "tick" mark from the check box
6) press "enter"
7) done and you can see the extension of your files now
