First, you'll need testnet ETH, which you can get from your preferred ETH testnet faucet. An example of an ETH testnet faucet is this one from MetaMask.
Secondly, you'll need testnet KEEP.
Use the KEEP testnet faucet in your web browser by adding your account address on the end of the faucet endpoint with the parameter ?account=<eth-account-address>
The faucet endpoint is:https://us-central1-keep-test-f3e0.cloudfunctions.net/keep-faucet-ropsten
For example, if your address was 0x0000000000000
you would paste this into your web browser:http://us-central1-keep-test-f3e0.cloudfunctions.net/keep-faucet-ropsten?account=0x0000000000000
The testnet KEEP faucet will issue a 300k KEEP token grant for the provided Ethereum account. This may take a few minutes to show up in your token grant tokens balance in the testnet version of the token dashboard.