You planter should come with 2 fertilizing spikes. I will send you another set, but you will not need to fertilize the soil until you see your plants flowering. The second stick is used once the fruiting bodies (the fleshy tomato part) have started growing.
PS: You can keep growing cherry tomatoes by continuing to add fertilizer sticks once a month. Your plant should produce tomatoes for up to 3 months (but I'd love to hear if yours produce longer than 3 months!) We use Jobe's brand tomato fertilizer which can be found at a variety of locations across the US. I've linked you the locator to find the stores closest to you.