With geocoins, there's a code on the back with a set of numbers. Then go to this page: http://www.geocaching.com/track/
Enter the tracking code at "Enter the Tracking Code of the Item:" and then click "track".
When you enter that code you can click submit a log entry. And pick what type of log it is then post it!
On your profile it should say that you've logged 1 trackable!
If you move it to another cache, make sure to log the same geocoin that you've moved it. If you do it on computer there will be a file below with all of the trackables (geocoins and travel bugs are called trackables) you're holding on to. Then you click dropped off when you submit the log entry.
Hope this helped!
-Blake Loves Willow
