Grace wrote:
I am doing a laboratory work write up and l have to insert
subscripts, for example as in hydrogen peroxide (H2O2) the 2 should
be a subscript.

Subscript and superscript are ordinary font formatting. There are checkboxes
for them in the Format Font dialog. There are also shortcut keys, Ctrl+=
for subscript and Ctrl+Shift+= for superscript.

For other sorts of symbols, see
http://word.mvps.org/FAQs/General/InsertSpecChars.htm.

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Regards,
Jay Freedman
Microsoft Word MVP FAQ: http://word.mvps.org