It's on the right side (passenger side)In addition to using the Key like you did (many don't know about that), you should also program a Pin Code into the little button on the hatch back door. Here is one of many videos, but it's a heck of a lot easier if you have the manual in had with instructions or someone reading them to you. It's very easy to do, but you only have so many seconds for each step.
This button that you program is not visible. It's to the left of the license plate. If I recall correctly, it's "shaped like a staple" (not round) and is not facing you - you reach it with your fingers just like you do to open the hatch door. If you do a search on this site, there are many posts/articles on it.