How to set-up Red Sea Bubble Counter :(

Hi All. Probably a silly question but I am about to set-up a new co2
system and purchased the Red Sea bubble counter. Anyone install one
(the Red Sea version)?

Question(s): Should there not be water within the bubble counter? If
soi, how do you get the water in it? How the fudge does one unscrew it
(to open it)?

Or should I simply just attach it and not worry about water being in
it? Red Sea has no instructions on their web site and the bubble
counter itself seems to be glued together with Crazy Glue.

Any help appreciated. I will ask where I bought it and will post if I
find out.
Cheers,
Bruce