Information for your correspondence can be gathered in various ways including researching the topic.  There are two ways you can go about getting the information:

• Primary research – this is research the you have done yourself.  It could be an interview, a survey etc
• Secondary research – is research that has been done by someone else that you can use.  It is important to note that should you use research done by others, they must be acknowledged for their work.  If not, you could be accused of plagiarism which is a serious offence.