An eSIM is just a physical SIM that has gone digital. Instead of you physically inserting a SIM into your phone to join the Mint network, you install an eSIM onto your phone/device. It means you don’t have to wait for your SIM to be delivered, you can activate straight after purchase.
If you are new to Mint, and have an unlocked, eligible device you can choose eSIM at time of purchase.
If you are an existing Mint customer, then log into the Mint app, head to Settings > SIM > Replacement SIM. You can check your phones eSIM compatibility on http://mintmobile.com/esim. Please not the device must be unlocked.