How is it possible to get resurrection candles?

The Mark of fallen which are the candle items used in the shrine to resurrect troops are items that you need to buy. You may receive a few as rewards from some events but in general you need to get them from packages.

When you tap on the shrine building to see your list of the dead troops you will probably see a banner at the top with the package to buy to get the candles. Or if you tap on the candle icon when you are trying to set the resources.