There are two ways to select curves: tap select and lasso select.
Tap on a curve or vertex to select it.
When a curve is selected, its control points will appear. You can tap on the control points to select a specific control point only.
Tap on the lasso select button to use the lasso select tool. Draw a lasso around a curve to select.
The lasso must completely enclose a curve (between two vertices) to select it.
After selecting an object, a move widget will appear. You can tap and drag the widget to move the selected object.
You can move a control point when it is selected. If two curves are smooth across a vertex, then moving a control point of one curve will influence the other curve.
Tapping the red button with a trash icon will remove the selected curves.