how to display fields in site from content query webpart in sharepoint 2010

You'll need to export the webpart, and add all the fields you want, then upload the webpart again to the webpart gallery.

Here is a step by step on how to do it: http://www.heathersolomon.com/blog/articles/CustomItemStyle.aspx

Mohamed Derhalli is correct if you're asking how to place a preconfigured CQWP on a page. (place on page, configure it, export/import).

But if you're asking about ways to get all the columns data, I believe your CT will have to be attached to a list and then data added to the list. Then configure the CQWP to read from the list with the CT and your slots will appear with your columns.

To modify the presentation of the data, you'll have to write XSL in a custom itemStyle.xsl (copy the original and link it in the .webpart file).

With 2010 you no longer need to export the web part to define what fields to include - you can do this via the slots when you edit the web part properties. However, Josey is correct that as none of the standard styles will display all your columns you will need to create a custom ItemStyle.

I have a couple of blog posts specifically on CQWPs and others on general XSL which will hopefully explain what is needed. http://paylord.wordpress.com

@Josey, If you add the content type to a list, and then configure the Content Query WebPart to read from this list, you won't have any advantage this way unless as I said in my previous answer, you need to export the webpart and make it "aware" of these new columns, then upload it again, it's something that you need to do in the same webpart's code, not outside it like in the content type or the list.