Highlight the characters you want to apply this to.
Goto the menu Format>Cells>Font tab>Superscript>OK
Note that Excel will only superscript TEXT. If you have, say, 102 and want
the 2 to be superscript then you have to enter 102 as TEXT. You can either
preformat the cell as TEXT or precede the entry with an apostrophe like
this: '102.