This article will help you find your SegmentIO write key. When used in conjunction with google analytics, this can help keep all your analytics data in one place.
First go to your segment IO account and click sources, then add source button:
Enter in the web URL and whatever you want to name it, and click add source:
Go to the settings button on the source page, enter in the info and save changes:
In the menu to the left, click on API keys and your write key will appear: