This feature is not in ePO 4.0 but is included in ePO 4.5, as far as I know.
I talked to the support platinum, and I was told that it would not be possible. So, please let me know how can I add machines by IP address.
In ePO 4.5:
Go to System Tree Actions and choose New Systems
In the Systems To Add box, enter the IP address.
ePO will look up the machine's IP address and add its name to the system tree. If you chose to send an agent install then this will be sent as well. (Note you can import a list of IPs from a text file as well - ePO behaves the same way.)
In ePO 4.6.0
If we add the IP address in Add Box, ePO will think the IP address as hostname. We can ping to the host, but it look like this step do not guarantee the ability to install agent in client system. That is what my experiment show.
Please correct me if I am wrong.