There are two ways that you can do it. The way I do it is by copying all of the text by the user I want to quote and then typing out quote user=“User Name” (including the quotation marks before and after the user name) in between brackets, then I paste the text that I want to reply to and then at the end of the quoted text, stick an /quote in brackets.
or
Follow this link: https://forum.freecapitalists.org/t/how-to-quote-a-post-in-a-reply-on-the-mises-forums/13847
I haven’t tried this method myself but it seems like it works for others.