If you need more help with spawning starfruit seeds, we have a detailed guide on our blog - click here to visit that page. Whenever you speak to a villager that says your name in dialogue (for example Gus at the Stardrop Saloon) you will be given the starfruit seeds item.
If you do wish to use this method, first set your character's name to when creating your save. You can only set your character's name once, at the start of the game (when you create your world), for this reason we recommend you use the animal name method. You will then receive the starfruit seeds item. To spawn this item using an animal's name, visit Marnie's Ranch, speak to Marnie and purchase an animal (we recommend a chicken as it is cheapest). updated This page is part of IGN's Stardew Valley Wiki guide and details everything you need to know about the item spawning cheat, including how to spawn items and a complete.
Spawning items in Stardew Valley is not done via commands, but rather through a cheat in which you must set your character's name, or the name of an animal, to the item code of the item you wish to spawn surrounded by.