Shields for SWFA by Sjet vs. Kerrigan, version 1.2 or 3.0, we can't decide.

Unzip this into your homeworld directory.  Now it gets interesting.

If you don't have any weapons mods installed:
Find homeworld\r1.script and homeworld\r2.script
Move them into homeworld\etg\
Now it will work.

If you do have weapons modifications:
Open homeworld\r1.script and homeworld\etg\r1.script
Find the chunk of homeworld\r1.script that sets the HitEvents for the four sizes of Energy Cannon and the four Plasma Bombs.  Copy these lines (about 40) into homeworld\etg\r1.script, overwriting the pre-existing lines.  There are a few lines between the Plasma Bomb hits and the Energy Cannon hits, so watch out for that.
Repeat with homeworld\r2.script and homeworld\etg\r2.script.
Delete homeworld\r1.script and homeworld\r2.script; they're not doing you any good.
Now it should work.