Hello there!

As you see, you`ll have to enable those two on the toolbar (1) ;
Select the path containing the nodes and deploy the Node tool

;
Select the desired set of nodes and click once more on one of them ;
After all of this, you`ll notice the change on the outer markers and center of rotation will appear (2) ;
Continue with the Node tool and place the center where ever you need it ;
Enabling Snapping will help you placing the center more precisely on the desired node.
Check
the Manual for some more info about the Inkscape, and welcome aboard!
