There are 3 main ways you can insert quotes.
Either press the
button on the top right hand corner of a post to create the quote automatically. If you have already started typing your reply then you can scroll down through the previous posts & click on the "insert quote" link in the relevant post to add a quote to your reply.
Secondly you can press the
button to create the tags when you are typing your post if you highlight the text in your reply you want quoted before pressing this button it will put the tags either side for you if not then you will have to cut & paste them into the right positions.
Finally you can just write in the tags either side of the text yourself.