Can I substitute frozen spinach for fresh in soup?

I’ve made lentil spinach soup a couple times, and the recipe calls for tossing in the spinach after the soup is mostly cooked, and just letting it cook for a few minutes.

I am in a frozen tundra for the next week and change, and there appears to be no fresh spinach, so I bought frozen. Can I use frozen spinach in place of fresh? Do I still add it when the soup is mostly cooked, or should I do it earlier? Or at the very very end, since it doesn’t really need to cook, just warm?