How to create secondary key!!

good day,

i'm using pgAdmin II as the remote client, after importing the text file
to postgresql database; i'm start trying to find the way to create the
primary key and secondary key. unfortunely, under the pgAdmin II there
aren't any tools to do that. However i managed to fine the way to create
the primary key by using the index function but i still cannot create the
secondary key in my database. please advise me!

Best Regards,

    /'"`\
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Nelson Yong
nelsonyong(at)ipmuda(dot)com(dot)my
THE BUILDING MATERIALS PEOPLE