Well, you've still not told us how far you get through Apple's instructions for setting upyour email (or where you go wrong with it), so we're struggling to help here.
Assuming that you can't get the automatic configuration to work, see the instructions under 'Set up your email account manually'.
If you're asked to choose between 'POP' or 'IMAP', select 'IMAP'.
If you need to enter the information for 'Incoming Server', type 'imap.plus.net'
If you're asked for the 'Outgoing Server', type 'relay.plus.net'
If you're asked to select an 'Outgoing Port', enter '587'
If you're asked whether 'SSL/TLS' should be enabled, select 'No'
If you're asked whether 'SMTP Authentication' should be enabled, select 'Yes'