Hola Stephen. When you say Present, Future, etc., you're talking about TENSES. Present tense, future tense, etc. I'd say there are four tenses you'll probably use most: present, imperfect, simple past (pretérito), and future.
To give one simple example using the verb hablar (to speak):
hablo = I speak (present)
yo hablaba = I was speaking or I used to speak (imperfect)
hablé = I spoke (simple past)
hablaré or voy a hablar = I will speak or I'm going to speak (future)
I didn't use the "yo" pronoun except with hablaba. In general, Spanish speakers use pronouns with the verbs only to avoid confusion or to add emphasis. In the case of all the examples I used except hablaba, the ending tells a Spanish speaker that the subject is yo/I. With hablaba, the same word can be used to mean I/he/she/you (formal) speak. To indicate which one you mean, you'd add the pronoun. Hence, *yo* hablaba.
I hope this helps.