There is a Partnership Desk on the Daily Recap.  In the top Menu (the green bar), there is an item labeled Partners. Hover your mouse over it, and slide down a bit to Partner Desk, and click.

You can leave a "postit note" expressing your wishes, or you can just look at other notes to see if any match your needs and contact that person. If notes overlap, you can drag them around however you like.

To register your wish, click "Write Note" and a form will appear. Fill out the form and press "Submit Form" at the bottom. (If you are not logged in, then in the last form field you must copy the displayed Security Code. If you are logged in, this field is not presented.)

Be sure to include your name, contact information, and what kind of partner you want. 

When your need is satisfied, you can manually delete your note or just let it expire. To delete your note, you must have been logged in when you wrote it, and logged in to delete it. There are little icons in the border of the notes -- hover over them to see what they do -- one of them is delete. If you are not logged in, you must just let the note expire.