To get tTAO to register your miner on testnet, head to Bittensor’s Testnet Discord channel and request tTAO! You will need to provide your miner’s coldkey.
You can purchase TAO from many exchanges, including Coin Marketcap and Changenow.io. Copy your wallet’s coldkey and send TAO to the address! Subnet registration is a variable cost, so be sure to factor this into your budget.