Objects communicate via inputs and outputs. When two objects are connected, their data flows from the output to the input.
Outputs are represented by dots, and inputs by arrows.
By default, objects have at least one output, represented by the grey dots on the right side of objects. To connect the output to another object, click and drag the dot onto a new object. The destination object will grow to indicate it can accept the connection.
A connection should appear, terminating in an arrow attached to the destination object.
To remove a connection, click and drag an arrow, and drop it in an empty space. The connection should detach.