Run a workflow on demand on a business process entity?

I would like to run a on demand workflow that runs something like this

If the business process workflow active stage is X

then update the active stage on opportunity-records to X

I have created the workflow, but how do I run it on demand? I know if I go to an opportunity view, I can run workflows from there, but apparently only if they are based on the opportunity entity. I can't see this workflow there. 

And if I go to view all processes, there is no option to run a workflow...  If this isn't possible are there any workarounds to update the opportunity records based on those criterias?

Thanks in advance for any input or suggestions.