how to change size of letters.

You could try the font tag. I think size can go up to +4.

 <font size="+2">Test</font> 

If your html just shows up raw when you type it in, it's because your using the Design Editor. If you want to code your own listing, click the "switch to text mode" link above the design editor.
But in the design editor, it's easy to change the font size. Just click on the drop-down menu beside "size", and from there you can select whatever size you want.

Thanks so much for you help.