Hi,
At the moment CST is not installed on my computer and I can not explain step by step by rote. But I can give you this clue, In CST you can specify points as field monitors and CST exports time varying electric or magnetic field graphs for the specified point in the coordinate system. Try to read the program manual carefully there shuld be excessive amount of useful information about this topic.
You do not have to match the time stepping. CST make some kind of linear interpolation to your time domain signal. I attached a drawing which explains your sample points with black dots and CST interpolation with red lines.
View attachment 138318