Just found the answer for this query.
Go to the developer site of Facebook and copy the like box code from there (both Javascript SDK and HTML). Then log in to your q2a website and then
Admin panel > layout > "custom HTML on side panel on every page" .
There you have to paste first the Javascript SDK code starting with <body> tag and ending with </body> tag. Just after that you have to paste the like box HTML code.
Then visit your homepage and you'll have you Facebook page like box on every page of your website.