I think the easiest way is to include a nodename field in your pod specification and assign the name of the desired node as value to this field.

There are other possible and more flexible ways to accomplish this, but I think they are more complicated.

If one needs to go flexible use nodeSelector, else use nodeName to be more rigid and run the pod on specific node

nodeselector 

Via Affinity: I think with nodeSelector is the simplest way to constrain Pods to nodes with labels.

Mhh, my limited understanding of this is, that you have to define a node label and a nodeselector for your solution.
The other procedure needs a nodename field only. A name has the node anyway.

But, as I said, I have a limited understanding and knowledge with this topic.