Quoting is a really useful feature. Simply find the post you wuld like to quote and then click the:

button in the bottom right hand corner of the post.
If you want to reply in that topic you can click add reply and it will automatically quote the post you selected above your reply.
It is possible to quote something in one topic and use it in another topic. All you do is click the quote button for the post you want to quote then click into the topic you want to reply in or start a new topic and your quote should appear.
When you click 'Add reply' or 'New Topic' your quote will appear like this:
Please note that the quote button does not work with 'Fast Reply'.
Your finished quote should look like this: