Good question. The way I handled it was to post a message in the "Public Faces of the OpNet" thread with a self-description, and included a link to a character sheet that I hosted from my personal website.
That said, you don't strictly need to have a sheet (unless you need one for your own reference); most folks here never post a sheet, and a lot of what is done here is pretty much seat-of-the-pants roleplaying.
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Time is the fire in which is forged the shape of things to come.