Going mad.... BCP, nodes, corners, conversions etc

I’m new to Glyphs Mini. And I’m going mad. The documentation isn’t helping.

How do I make the BCP handles appear, please?

Also, “enter” is not changing blue squares to green circles.

Thanks in advance.

Option-click on a segment (=the black line between two nodes).

See the Drawing Paths video on the Get Started page. Or the Mini Handbook, Section 2.3.4 Converting Nodes and Segments on pages 13 and 14.

Thank you!