1 1/2 spacing

[C. S. Kan]

I am running the latest ver of Lyx for windows on windows 98 with Miktex. I
would like to set the line spacing to be 1 1/2 spacing and found the
following error:

setspace.sty not found.
\onehalfspacing

Is there any where that I could get the setspace.sty? How do I install it
into miktex?

Thanks. 

Kan