Plant in a location that enjoys full sun and remember to apply water fairly sparingly. Keep in mind when planting that Mexican Zinnia is thought of as tender, so it is really important to plant out well after your last frost date.
Growing Mexican Zinnia from seed
By our calculations, you should look at sowing Mexican Zinnia about 21 days before your last frost date.
Transplanting Mexican Zinnia
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Mexican Zinnia is a tender plant.