I have a website, www.example.com. I have a subdomain, subdomain.example.com/ that contains all my website's landing pages. Do I have to add subdomain.example.com as a new property in Google Analytics to see my landing pages, or is there a filter I can create under the www.example.com property that will allow me to see the subdomain landing pages (i.e. subdomain.example.com/landing-page)?
I would create a new View under the same Property and apply a Filter to only include that sub domain.
In your Google Analytics Account:
1) Click on Admin button - Make sure that the right property is selected
2) Click Create New View - Third column on the right.
3) Create your View
4) With the sub domain view selected click on Filters
5) Enter Filter Name - Filter Type [Predefined] - [Include Only] - [traffic to the hostname] - [that contains]
6) Hostname [sub.domain.tld]
In Classic you also need to go to Tracking info and turn on the sub domain tracking option and then update your tracking code. It will add a line that looks like this: