BES is a corporate system, a company would have a Blackberry server installed and the company bbs go through that. Enterprise activation is for this, this is not what you want, unless you are going through your work.
You need the BIS, or Blackberry Internet Service enabled on your tariff (which is likely to already be on I'd have thought).
Then your mobile provider will probably have a website you can go to which will let you associate an email account with the device.
For instance Vodafone's site is
http://mobileemail.vodafone.net/
Once you sign up and put in all the details the emails account will appear on the device.
It can be tricky to understand at first that with Blackberrys using BIS the configuration of an email account is not done on the device at all really
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