If you need to have this software first in your PATH run:
echo 'export PATH="/usr/local/opt/icu4c/bin:$PATH"' >> ~/.bash_profile
echo 'export PATH="/usr/local/opt/icu4c/sbin:$PATH"' >> ~/.bash_profile
For compilers to find this software you may need to set:
LDFLAGS: -L/usr/local/opt/icu4c/lib
CPPFLAGS: -I/usr/local/opt/icu4c/include