(This question is for people using Mail on the Mac. If you are using Outlook you can find a guide for that here. Other email clients are available.)
If you have not used Mac Mail before it will ask you to enter new account details straight away. Otherwise use click on the File menu and select Add account.
Type your name, email address, and email password.
This method copies messages from the server to your personal computer.
Fundamentally, think of it as "store your email on your computer".
A pro of this method is that you are not subject to the server storage limits on your computer.
A con is you cannot reference emails easily on multiple computers, and if you wish to use webmail, only the emails that haven't yet be downloaded to your computer will be available.
This method leaves email on the server, for access via Mac Mail, webmail or your phone. Is has more features than POP and all folders such as sent and received will be synchronised between any mail application you wish to use.
A con of this method is that you are subject to the server quota for your mailbox size, so it's recommended that you download or delete emails that are no longer needed.
Enter a description for the incoming server
Enter the incoming mail server which is mail.yourdomainname.co.uk
Enter your username which is your full email address
Password: enter your email account password.
You may get a verify certificate box, this is normal
Click "Show Certificate"
Tick "Always trust "server name" when connecting to "mail.yourdomainname.co.uk"
Click continue
You'll be then shown an account summary