sorry, I should have given more details.
I simply want to make that set of vertices into a circle on the same plane, rather than a square.
The reason is that I created the conic form using the polygon mesh, then weld method as described in your demo video for tensile form finding https://www.youtube.com/watch?v=-Wxzb7MhdVw
This leaves the open top of the mesh as a straight edged mesh with corners, however, I would like this mesh to go from a square base to a circular top - then optimise for springs.
So, I want to keep the mesh connectivity as it is, just use some sort of curve fairness to make the top a circle.
I'm sure it's a simple task with the correct tool, but I am pretty new to Rhino etc. Sorry for a pretty dumb question!