Before I proceed with removing one of my MetaTrader accounts, is there anything I need to be aware of?

Yes, there is. Once you have removed one of your MetaTrader accounts, you will not be able to recover the account again. The action is irreversible.

Also, you would not be able to remove an account that has a negative balance. Once that account balance has been brought to zero (0) you will be able to remove the account.

Where do I need to go to be able to remove one of my MetaTrader accounts on my Asgardian account?

You will need to tap on My Accounts.

Tap on the account you would like to delete. 

Tap on the three dots next to your account number and select Delete Account

A notification will come up just to make sure you haven't changed your mind.