This can be done from either the web client ( http://www.livejournal.com/editjournal.bml ) or by using the Windows client. If you have not yet downloaded the client you may do so at http://www.livejournal.com/download/ .
Should this be changed to reflect the fact that many LiveJournal clients support this functionality?
I'd suggest a rewording like this:
This can be done from the web client ( http://www.livejournal.com/editjournal.bml ) or by using one of the available LiveJournal clients that supports this functionality. Some clients that support this are the Windows client, [a Unix client, a Mac client, ..., ], which can be downloaded at http://www.livejournal.com/download/ .
or something that preserves the primary reference to the Windows client, if necessary:
...or by using the Windows client or a client for your preferred platform that supports entry editing (check the homepage or journal for the client to determine whether it supports this functionality).
Is it even correct to refer to just "the Windows client"? I know a lot of Windows users use the Semagic client instead of the "regular" client, but I'm not sure how references to those should be handled.