Nad.fun is a new interesting activity in the Monad ecosystem.
If you haven't started working on Monad yet, then first you need to add the Monad test network, and request test tokens on the main page:

https://testnet.monad.xyz/

Go here to apply my referral code 
https://testnet.nad.fun/ref/KFZ4VK

Go to the "Create token" tab - create your test token (add a picture, write a name, ticker, description).

Sometimes the transaction does not go through, it says that there are not enough funds to pay for gas, then just click Edit gas and remove the extra numbers at the end