While attacking, you may exhaust this card and spend 1 die to change 1 of your dice to a face with an Accuracy icon.

Does this mean that I would get rid of one die and change another one to an accuracy? Or can I change the one I spend to an accuracy?

Spend = remove from pool.

And you can spend a blank die....

And you can spend a blank die....

Also note you spend an accuracy dice to cancel a defense token.