Right now, we support verification only for one single solidity file - therefore, before deployment and verification, you will need to flatten all solidity sources to one file.
To flatten your solidity files we recommended to use Truffle Flattener lib.
npm install truffle-flattener -gtruffle-flattener <solidity-files>
Or you can use any other flattener lib.
To easy the verification we recommend the contract deployment using Harmony Remix.
You can verify your contract here: https://explorer.harmony.one/verifycontract
It is important to use the correct parameters (same as on deployment):
Chain Type (mainnet or testnet)
Then click on Sumbit button. If all params was correct - you should to see Success message, or Error if bytecodes are not equal. On Success case - you contract will verify and you will see all contract details on contract explorer page.