its in the same pop-up menu when you copy a branch but choose node, then choose attach property, then choose nialpha channel.
or just click on an alpha channel in another LH and choose copy, thn paste in yours.
OK, I did, but nothing happens. It looks the same. I mean, it's not like it is a big problem (or not a problem at all actually), but still the eyes seem to look a little "weak" after doing what MO said. They no longer turn red, though.