You have two options:
1. If you have fields in your form with the appropriate names for mailing (SendTo, Subject, Body, etc.) just put the recipient's name in the SendTo field and use @MailSend without parameters.
2. Use @MailSend with parameters and put the field name that contains the recipient's name in the first parameter, i.e., @MailSend( sendTo ; copyTo ; blindCopyTo ; subject ; remark ; bodyFields ; [ flags ] ) - just replace the generic parameters here with the actual field names from the form
Look at the Notes help for @MailSend - it is pretty straightforward