Import and Edit an STL and trying to round the edges

[Anonymous]

Seems like this should be simple, except I have about 1 hr under my belt in 3D design...
Download the rocket from Thingverse. Import the STL, select it and convert mesh to BRep.

What I am trying to do is round the vertical corners of the fins in the "base".

I have tried to select the edges and fillet or chamfer and I get an error

  The fillet/chamfer could not be created at the requested size. This might be occurring at the ends of the selected edges.
Try adjusting the size or using multiple separate operations. Check that the selected edge chain ends at a sensible position, and if not try selecting more edges.

I am guessing I need to combine several of the facets to create an edge to chamfer?

I am pretty much out of my element and would like some assitance

[TheCADWhisperer]

I recommend that you forget about editing someone else's stl work and simply create your own design from scratch.

[Anonymous]

Since that would be a huge learning curve, I prefer to take it one step at a time.

And I figured out

https://www.youtube.com/watch?v=NTWZU-mPtw8.