>I need to use some symbols like the Alpha and Beta....
>How can I do ?
>

Select a font that has these characters, and use that font to display the required text. The Arial font contains at least some of the necessary characters, and you can order fonts with the necessary character sets from a company like Adobe (their mathematics fonts should have the ones you need, or a Greek alphabet font, etc.)

You will have to buy a font if you don't currently own one that will provide the characters.