Add on domain not indexed but only folder has been indexed

I have an add on domain but the website is not appearing but instead only the add on domain was indexed in the form of subfolder.

For example,

my main site is www .main.com and add on domain is www. addon.com

In google, www. addon.com is not indexed but www .main.com is indexed.

How do I correct this?

thanks

 

build more links to your addon. I have about 50 add ons and counting now and most of them are indexed without a problem.

Here's how I got indexed in less than three days

 

Thanks. Today it has been indexed.