You'll know alright - it's quite runny, more so in warm conditions. It comes in varying forms of container, all have a probe of some description. Squirt it in, move the frame about, or leave at different angles over night, the surplus will flow from every orifce - best done as a bare frame, although it cleans off with white spirit easy as anything. Then, ideally top it up with a lighter application every couple of years, as recommended by some of the companies below.
I haven't used Framsaver, but assume it's a similar cavity wax but black, you can get black Waxoyl now, but I prefer the er...wax coloured!
Top frame builders spray cavity wax in their frames from new; Indy Fab, Soulcraft, Roberts and even Singular I believe.