Select the exponent, then Format/Text Style... Superscript (see picture). Press Alt if the Menu Bar with Format is hidden.

the exponent is my signature in emails, letters, etc., b cubed, could you make your instructions more simple? and do not leave anything out! for example, i am in an email and i type b (now how do i cube that b as my signature in the email?)

Creating a signature is covered here, but the process of making super or subscripts is the same:

type b3 and a space

select the 3, then Format/Text Style, select Superscript

press the right-arrow key twice to continue typing