To extend a user profile, so that profiles contain more information that you might need for your users, log in as administrator and from your Administration dashboard, visit Extended Profile section. Over there you will be able to view a tabular list of all the custom defined extended profile fields.
Click on the Add Field (1) button to create a new profile field.
Fill in the required information, which are a name for this profile field (best practice is to give a name in lower case and without any whitespaces or symbols) and the label for that field.
Then for the Create for option (2), select Users. This means that the extended profile field you are going to make concerns users. That's it.
This field will now appear in your users' profile (3).
New users that will sign up in your system will have to fill in data for this field if you choose it to be mandatory. If you have chosen this field to be visible in reports, data from this field will also appear in your Reports.