Hi @mrhankeh,
If you want to use your own account/key manually you can view/edit the key by doing this command:
cd /var/EZSTEEM/steem/programs/steemd/witness_node_data_dir && sudo nano config.ini
In the file, search for the tag witness. Set your witness and miner to the same account and enter the private key with the miner. eg

# name of witness controlled by this node (e.g. initwitness )
# witness =
witness = "YourAccount"

# name of miner and its private key (e.g. ["account","WIF PRIVATE KEY"] )
# miner =
miner = ["YourAccount","5K847LgAEW6qsm6BwhorGRgNotARealPrvtKeyownLjTwQLzzKQ"]