FTD does not support multiple contexts at all so you cannot configure it.
For "active-active" the closest you can come as of the current 6.2.3.x release is clustering (for a given (single) FTD instance).
Look for this to change in 6.3 later this year although the model will be quite different (containers not contexts) and it will only be on Firepower 4100 and 9300 series.