How can i bold, color, and make the text bigger?

[-->Rebecaaa]

Example: <center> = to get the words in the center.
But i can't figure out how to color, bold, and make the text bigger at the same time.
Please HELP me !

 

[xx.lysss.xx]

im not sure bout color.
but to bold is <b>
and to make text bigger is <big>