How to manually sign network contracts.

Make sure that the Order you're trying to activate has the status "Awaiting manual activation".
Locate the Network Contract by opening the side-tab called "Provisioning".
Make sure to select the correct Network Contract from the menu, it should have a button called "Sign" in the right-most column. This can also be deduced by the fact that the "Terminated" status is "No".
You can now either press the "Sign" button in this view, or you can press the contract number (the number in the left-most column) to inspect the contract and make sure the provisioning parameters are mirroring what your provisioning system is supposed to send.

In this example, a 100/100 service is being provisioned, and the parameters for download/upload speed here look correct.

If your order has the note, "Awaiting manual sign" this artcle will help you resolve it.