Can I use the licence on trial/challenge accounts in FTMO?

If you have a licence in your name then in FTMO you will not be able to use it. FTMO labels all accounts with a standard name and there is no way to distinguish who the user is. For TRIAL accounts, you will find downloadable keys at Updates | Demo versions. For CHALLENGE / FUNDED accounts, you can buy a package of 5 licences per account number and add further numbers as you progress in FTMO.