To stake your funds with the Blockdaemon staking pool, you can use the Post Stake Intent endpoint.
This endpoint returns an unsigned transaction that needs to be signed and broadcast to the network. The signing should be done with the private key corresponding to the public key in the Stake Intent, which holds enough UTXOs for the stake amount.
If the staking period is not specified, the staking period will start now +5 minutes, and the end time will be the validator expiration time. Each validator is valid for a maximum of 1 year.