Depends on the quality of the LR, how it has been handled and to some degree on the size of your tank.
If the Tonga LR it is uncured and has lots of die off (stinks pretty bad) cure it in a separate container for a few days with lots of water changes, then add it to the tank along with part 1 of the package. If the LR is fully cured or is from someone else's established tank, you can add it along with part 1 or 2 of the package.
(Edited to correct spelling mistakes...)