The main site is the only place to activate the support license. This means your options are:
1) Don’t activate the support key (which means you’ll need to manually update the plugin because 1-click updates will not be available)
2) Activate Event Espresso on the main site where you’ll be able to activate the support license key. Once the support license key is activated you’ll be able to do the 1-click updates from the Network > Plugins page.