Seems to me that it explains the process pretty clearly, but if you have any specific questions after going through the steps there, then maybe we can help. Though you would probably get better and more specific help from one of the support groups listed on the winlink.org website.
Airmail will now have both Sailmail and Winlink capability. You will find the Winlink station list available in Airmail. Just send a radio-email message to yourself via one of the winlink stations to get started (as is described in the Winlink web page in denverdOn's post above).
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA www.sailvalis.com