Copy the plist to
~/Library/LaunchAgents then run
launchctl load ~/Library/LaunchAgents/com.scripting.opml.plist
This plist assumes that OPML Editor is installed in
/Applications/OPML. If you have it installed in a different location, you will need to modify line 13 of the plist.
The OPML Editor should launch. It will re-launch within 10 seconds if it quits for whatever reason.
To quit OPML editor (and keep it that way), use launchd.
launchctl unload ~/Library/LaunchAgents/com.scripting.opml.plist