We use the \begin{quote} \end{quote}
command, which automatically
indents material from both sides.
The following example, drawn from OUP's Edpress News
``It's is not, it isn't ain't, and it's it's, not its, if you mean it is. If you don't, it's its. Then too, it's hers. It isn't her's. It isn't our's either. It's ours, and likewise yours and theirs.''
is achieved by:
\begin{quote} ``It's is not, it isn't ain't, and it's it's, not its, if you mean it is. If you don't, it's its. Then too, it's hers. It isn't her's. It isn't our's either. It's ours, and likewise yours and theirs.'' \end{quote}