Marketing Events are like post-its for your analytics. You can create a Marketing Event to record the date you launched a marketing campaign so that when you look in Sources months later, you'll see the note and know why you had a spike in traffic and leads.
1. Go to the Sources Report
Find the
Sources report.

2. Add a Marketing Event
Click the
Add Marketing Event button that's below the filters to the right of the Sources graph.

Then enter details about this Marketing Event, and then click
Save.

-
Action Date - The date the campaign launched
-
Action description - Briefly describe the event so you can remember what it is later.
-
URL - If it's a campaign that lives online (banner ad, guest blog post, etc.), enter the URL.
3. Look at Marketing Event in Sources Graph
To see your Marketing Events in your Sources graph, look for the calendar symbols below the bars of the graph.

Click on the calendar icon below the date for which you just added your marketing event to see what it looks like.

Now you can identify causes of spikes in traffic and leads!