Q: Trying to write a long set in curly braces where the set is going to be two rows I'm basically trying to recreate this:

I've tried creating an array and using the \left and \right commands but I keep getting the error:
"\left can only be used in math mode" So I was wondering if I even need to use an array or do I use another command?

A: If you're getting a message that \left can only be used in math mode, that means you're not in math mode. So have you enclosed the whole of what you're working in \[…\]?
I would be inclined to do this as:
\[
S=\left\{
  \begin{array}{l}
  1324, 3124, etc.\\
  2314, 2341, etc.
  \end{array}
\right\}
\]

