find my Ipad question

Okay so I downloaded my Ipad2 with the "find my Iphone app." I tried it and was impressed. I am to understand that this free to use. Okay so it works fine from my Ipad. However I already know where that is.(right in front of me.) So I tried to locate it from my macbook pro. in the other room. To no avail. I went to the mobile me website and signed in with my password, but does not seem to recognize it. Nothing happens beyond that. I know I must be missing something on this. Any suggestions? Obviously this new to me. Thanks.

Thanks Chas. It works fine now. I was not sure what I did wrong, but it's all good now.

Find my iPad works quite well. Just tried it.