How does one pronounce the '@' symbol?

How can I pronounce @ symbol: At / At the rate?

The "at mark", "at sign", or "at symbol" is its usual name. According to Wikipedia its official name is "commercial at".

Can I use it in a sentence? Please explain with an example.

It has no function in English sentences.

"At" as in "my email address is name at domain dot com."

At sign

The at sign (@), also called the ampersat, apetail, arroba, atmark, acosta, at symbol, commercial at, curlat or monkey tail, ...

If you would like to mention the symbol by name, ampersat seems to be the most easily recognized among its many names.

UrbanDictionary and GoogleAnswers mention that it is also called the 'amphora'.