carolyn -
someone will correct me if I'm wrong
the reference WO12 is for Muster books; now from memory these are very large bound volumes and it's possible you will have a long trawl looking for your man with little information at the end of it, these books were used for the day to running of the Regt.
If you can find him you should get name, age, place of enlistment, trade but no birthplace! after 1863 and up to 1883 you should get any wife or children but only if they were in married quarters.
You're better off to try for Attestation or discharge papers, (these should be filed together) and they will be in a different series.
See if you can get one of the guides to records in the PRO from your library, there is a separate one for the Army, failing that try for Tracing your Ancestors in the PRO by Amanda Bevan,
Suey