If you need to install the agent but wish to wait to register it to a HUB, you can do so with the following steps on your agent:
1. Download the agent from the HUB:
wget https://<IP.ADDRESS.HUB>/installers/ossec-installer.sh
2. Change the permissions of the installer
chmod +x ossec-installer.sh
3. Run the installer with the flags indicated
sudo ./ossec-installer.sh <IP.ADDRESS.HUB> --install-only