I need to add calcium to our pool and I think I need to do it soon. (concrete/plaster pool Calcium level at 100)

I have been keeping my chlorine level high during the conversion process so my questions are:

Is it OK to add calcium with a high chlorine level?

Is there a better time to add it day vs night?

The bottle says broadcast around pool....is that the best way to add or should I add at the skimmer?

Should I add it all at once (I will probably need about 20 pounds) or add in intervals?

Should I wait for a certain number of days to backwash once it is added?

Thanks!