This is a short introduction to KMail and its usage so you can start working with it right away. Please follow the links to find detailed information on the tools described here. For more in-depth information see the Using Kmail section.
When KMail starts for the first time you will be presented with the Account Wizard to set up email accounts.
Easily import your emails from other applications with the Import Wizard
If you are moving from another KMail installation, e.g you want to transfer your KMail to a new computer, you can use PIM Setting Exporter to export everything from your old KMail installation and then use it again in your new installation to import the items you exported.