If you're talking about materials provided by Straight Talk, I would pretty much skip those and head straight to
YouTube (I'm not slamming ST, but a lot of the manuals, etc., which are produced by parent company Tracfone, tend to be rather vague, at times).
Also, an important question is "is the Straight Talk SIM an AT&T or T-Mobile SIM?" (I am guessing AT&T, if you are using the iPhone -- if that's the case, you should find some good video tutorials on it from YouTube).