In the Send Mail item in the FIleMenu and in the Script step also called Send Mail, there is an opportunity to calculate the To, From, CC, BCC, Subject & Body.Look at the right of the fields for each.
There is also an option to send the email as a single-record email or to send one for e each record. Using the second option you can insert data like names and email addressses etc.
Lyndsay is correct you can use calculation fields and that will work fine.
I prefer to use variables to collect the data that I need and then in the send mail set up use those variables to fill in the appropiate fields.
Either way will work it is just a matter of preference