Your statistics can tell you useful (and interesting) information like where people have come to your website from, then you can drill down and see which promotions are working for you.
For example, if you post on Facebook about a new product available on your website on Wednesday and link to it, you can jump into your statistics a few days later (giving people time to see/act and your statistics time to catch up) and see how many people viewed the product on and a few days after Wednesday coming from Facebook.
Log into your Google Analytics account.
In the left menu go to: Traffic Sources > Sources > All Traffic
Change the date range the graph is showing to the days you would like to see results from.
In the main graph area
Click on facebook.com/referral in the list of referring sites
Inbetween the graph and referring sites (which should now only show Facebook) there's a little dropdown menu that says 'Other' (next to Primary Dimension: Source/Medium), click on that and choose: Traffic Sources > Landing Page
This will show a list of pages under the graph. The list shows which link visitors from Facebook clicked on.
Find the link to the product you promoted and you will see the amount of visits it has had in your chosen date range from Facebook.
