First off, welcome! I'm not sure that this is what you mean, but you can create a 'profile' which might establish the nickname. I have a question in for you on that. Meantime, here are the instructions to make a profile:
Can I change the name of my Tag profile?
Yes. Log in using the Tag profile that you would like to change. Click on the Settings button in the top right corner of the LeapFrog Application window to open the Settings window. Click on the Tag Reader tab, enter a new Tag profile name, and click the Apply button. Note that your Tag Reader does not need to be connected to make this change.