1. No. You ordered them without an OS.
2. No. Must be purchased with the system.
You have two options:
1. Return them, then repurchase with an OS.
2. Purchase a Retail Windows license for each machine.
You may be able to work out a deal with a local system builder to sell/repurchase with OEM license (generic/Microsoft OEM which is a lot cheaper than full Retail), but the system builder's cost on deal like that would probably make it the same as going with Retail in the first place. You can't purchase generic/Microsoft OEM software for your own machines.