So, when do you use "yo"? Well, it's quite simple really, you use it when you're talking about yourself, just like you would with "I" in English. For example, "yo como una manzana" means "I eat an apple", and "yo vivo en España" means "I live in Spain".
But, here's the thing, in Spanish, the verb conjugation often indicates who is performing the action, so you might not always need to use "yo" explicitly. For instance, "hablo español" means "I speak Spanish", and you don't need to say "yo" because the verb conjugation "hablo" already implies that the subject is "I".
