Math font size

[Lyx Physicist]

Hi, I have inserted a few equations using the math panel and I want to
enlarge the font so its easier to read.  I tried to just highlight the
text and make it bigger, but that didnt work.  Is there something else I
need to add or some other menu to do this that I havent seen?  Im
running lyx 1.4.  Thanks, 
Charles