ACP > Users & Groups > Mass Mail. Follow the steps, should be quite clear, and if you're stuck on a bit, try and be a bit more descriptive than 4 words
there is 2 option for Send Mass Mailing
1. Define the HTML Message
2. Define the Text Version
which one should i use. then about username contain and email contain in next step.. What should i put in the text field
You choose. If you choose the one that says both, it gives you the option to make it generate the text version automatically.
And for the username or email bit, you don't need to put anything in there if you don't need to, you just choose the areas you want to define recipients by. Usually by usergroup I'd imagine.