How do I configurate my computer to allow me to get emails using my apple account?
iMac, Mac OS X (10.5.8), Processor Name: Intel Core 2 Duo
Instructions for you here > Configuring Mail for your email account
You can set Mail up manually to access emails in an existing iCloud account - you cannot create an iCloud on Snow Leopard (which I assume is what you have, despite your signature saying you have Leopard?).
The setup process including the server settings is described here:
Entering iCloud email settings manually in Snow Leopard or Leopard
How can I use my apple email address to send and receive emails?
