How do I access Find My Friends from iCloud.com?
You can't to my knowledge. Find My Friends (sadly) requires an iOS or OS X device be configured for use with Find My Friends at least once. If you have no Mac or iOS device, you can't. If that article wasn't clear enough (it's rather vague) here's a more explicit one.


  Note: If you don’t see Find My Friends on iCloud.com, your account just has access to iCloud web-only features. To gain access to other iCloud features, set up iCloud on your iOS device or Mac.


After you do that, then you can access it from the web.