Fill the tank level up and crank the co2. If you have a drop checker, make sure its nice and yellow. Your also going to want to make sure ferts are enough so estimative index is a good start.
If you don't crank the co2, a lot of the HC will die off and start to yellow. Expect it to take 2 - 3 weeks for the HC to adapt before you start to see some growth.
Each week, slowly dial the co2 down until you eventually reach normal levels, or whatever you desire.