Look at the top right hand corner of the post you want to quote, click on quote, then either delete any bits of the quote you don't want (leave the words quote at the front and end) then type your reply underneath
for instance the above would look like the following with the addition of [ and ] at either end
quote="Standard_Bearer"]Can you clever B***ers tell me how to put quotes into boxes when replying to posts![/quote
Or if you press the quote button in the reply page (see below), it gives you a quote followed by a /quote on the second press, put it at the start and end of your text, add an ="user" if you want to refer to the originator of the text...