To add a measurement, select the desired measurement type and insert a measurement. Once the measurement has been created it will be selected by default. To exit the measuring session select the Exit Editing Mode button. To delete the measurement, select the Delete Measurement button. Multiple measurements can be created in a single editing session. Once you have exited a measuring session a measurement can be deleted by double clicking on it. This will select the measurement and reactivate the measurement editing toolbar.
Further Reading on Measurements
Measure Distance | Point-to-Point