I’m not sure what software you are using or what the error is describing. However, for making a TestNet asset, I would highly recommend the LaylaCoin Tutorial by @liz. It’s a really great and straightforward path to creating TestNet ASAs.
Welcome to Algorand!
transaction ... overspent
indicates that you did not fund your account.
You can also see on the left that the balance is 0 Algo.
You need to fund your account on TestNet using a dispenser: