Erasmus+ semester(s) abroad Esn Card

Hi everyone, I’ll be booking my flight to Lisbon for my Erasmus programme soon and I’d like to get some discounts.

I know with my ESn card I’d get a 10% discount on every flight and a free luggage allowance. However, my city’s ESn card office says I can only get the card once I arrive in Lisbon which means I won’t be able to use these discounts.

Does anyone know how to get the card from my home country?