First time you open sylpheed, you will see the following:
if you have made an account before, you can open this window from Configuration>Create New Account...
choose IMAP 4.
Now enter your personal information, replace Display name with your name and replace email address with your email address. make sure to enable SSL on both IMAP server and SMTP server.
put email address as your User ID, imap.ircnow.org as your imap server and smtp.ircnow.org as your email address.
you are done, enter your password.