Greetings. You are at the home of K-Meleon. K-Meleon is an extremely fast, customizable, lightweight web browser. This site and forum have nothing to do with Yahoo mail, it's unfortunate that search engines link to this forum so quickly when people search for "compose mail in yahoo".
You should probably visit the following pages or search for a tutorial in your native language.
http://help.yahoo.com/tutorials/mmail/mmail/mm_compose1.html
http://help.yahoo.com/l/in/yahoo/mail/yahoomail/basics