Yeah, you say this is a tutorial that new people to modelling to follow, yet you neglect to explain the basic stuff. I mean, I've used C4D before so I know where the spline tool is, but others might not... since C4D is nicely icon-based a little pic of that would help. The model might be basic but you assume folks know where everything is.
Once you've set the selection, it'll place a little red/orange triangle next to the object's name in the object manager. Click it and it'll open it in the properties pane. You'll find the name there, most likely named "Polygon Selection". Just change it there.