convert OR and SE in GCTA-COJO analysis

Hello,
I'm pretty new here.
When I read GCTA user manual for COJO analysis, I found a note said "For
a case‐control
study,
the
 effect
size
should
be
log(odds
ratio)
with
its
corresponding
standard
error". 
Previously I got GWAS association data from PLINK with OR and its standard
error (SE). I wonder how can I convert this SE here, when after converting OR to log(OR)?
Thanks
Shirley