verification confusion

I am slightly confused about how this works, I have my site registered on google webmaster where a sitemap has been uploaded but Google can’t find my site.

I have no code because it let me upload straight onto webmaster without having to do that. The blog I want to be picked up is a subdomain of my main site which is picked up by google. Do I need to get a html code to insert? if so, how do i get one when google already has my site on webmaster?