Hi @Mannu & welcome 
The Railcard is purchased through Trainline (website), using a discount code generated by Monzo. I’ve purchased 2 railcards with a Monzo Max discount - both using the Trainline website to buy.
To see the connected railcards in Trainline:
Web (https://www.thetrainline.com/): Log into your trainline account, click on your name (top-right), click on ‘My Account’, then click on ‘Passengers & Railcards’ to see active and expired railcards.
App: (Android), from the Trainline app, tap on ‘Account’ and then ‘Railcards’ in the ‘Booking preferences’ section to see the active railcard(s) in your Trainline account.