To do an IOC scan, you do...
IOC = Indicator of Compromise. E.g. file/hash/regkey/whatever that means "they got to this box"
IOC scans are very intensive scans intended for "incident response situations", where you're digging for bad actors in your network.
If you mean you're trying to do an old-school "virus scan" there isn't really a way to do "scan all of my machines right now."
You can do them one at a time, or add a scheduled scan to the policy with a time that's soon...
Keep in mind a full scan will eat up CPU.
There's also a philosophy that you shouldn't have to do a full scan... if its hit the box after install Secure Endpoint should have seen it.
(yes, I know there are issues with that... just letting you know what I know)