Present/Future/Past Tense in Korean
Hey! So I have a question regarding the tenses in Korean (present, future, past). I read before that to make a sentence present, you would add the suffix -yo (I have to use romanizations...my computer can process Korean but can't type it.

) to the verb/adjective. For instance, "It's cheap" would be said as "Sayo" correct? It "presently" is cheap.
However, I also read that to say something is present, you would put "neun" after the subject. For instance, "I know him" would be "Na neun geu namja ahneta" Literally, "I am knowing that man."
Does it matter which one I use, or is there a rule that says when you use "neun" and "-yo"? Is one of them wrong? Please help: I'm confused >.<
As an added bonus (you don't have to do it, I just would be very grateful and would love you forever~~) how do you turn things into future tense and/or past tense?
Basically, what I'm asking, is: How do you turn things into present tense (and if there's more than one way, like the two I listed above, when do I use each one?)
Bonus: How to make things past and/or future tense?
Thanks everyone ^.^