You mean a glass diffusor with a ceramic disc?
If so then you want to get some CO2 hose that is long enough to go to the CO2 source (yeast/pressurised)
(airline hose will suffice until you can get some proper CO2 hosing but be sure to get the right stuff as airline hose is more susceptoble to leaks and porosity)
Then if you have bubble counter/NRV then cut it in the places you want to connect to.
Once its all connected position the diffusor with the sucker(s) in a corner of the tank prefereably underneath your water output.
You are connected and ready to go. Will take time to build up the pressure with yeast, pressurised will take a few minutes.
Clean it at least fortnightly by soaking in bleach for 5 minutes, then rinse thoroughly, then soak in dechlor water for 5 minutes. then again for 5 minutes in some fresh dechlor. reconnect
Andy