sending email to new user after user created.

I have a register user window with first name last name user name and email, then i have sewcond database table called user_profile with user id last name and first name. Everything works create user update the first name and last name in the user_prfile table and send email to new user with welcome message and their password but i can not figure it out how to get the first name and last name in the message body with their user name and password. i have the mail definition bodt text file. Thank you for all the help.