I think you would just sign into your Gmail account from your computer to get location. And your phone should be signed into your Gmail account from activating it.
Here are the Plan B instructions at market.android.com:
1. Install Plan B to the phone that you are trying to find from the Android Market website: https://market.android.com/details?id=com.lookout.labs.planb.
2. Plan B will start automatically and send your phone’s location to your Gmail address.
3. To locate again after 10 minutes, borrow a friend’s phone and text the word “locate” to your lost phone.
Good luck! Let us know if it works.
Sorry to hear you lost your phone. In regards to tracking a lost device, unless you had a third party application installed on your phone prior to losing it, we are unfortunately unable to physically locate it.
We do have the ability to place your lost device on our lost/stolen list which will restrict anyone from currently using it and prevent any future use of the device as well.
Also if you have insurance on your phone you can click on the link provided below to file a claim. http://bit.ly/07CrqPK
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