Add a pin:

Drag a pin from the right hand side onto the chart.

Remove a pin:

Right click on the pin you want to remove.

Move a pin:

Click and drag a pin to its new location.

Connect two pins:

With shift held, click on two pins to connect them with a line. This will also show the difference in each of the pins properties (e.g. pressure, enthalpy, etc).

Disconnect two pins:

With shift held, click on two connected pins to remove the line between them.