Harpists usually move the pedals in such a way that they do not make the strings sound. However it is possible to produce a pitch solely with the pedals without plucking the strings.
The pedal is pressed energetically, making the tuning disc hit the string to produce a tone.
The sound of pedal notes is rather soft. Remember that the pedals move the respective tuning discs of all octaves simultaneously. The strings of the lower octaves sound more than the higher ones and therefore dominate the total sound of the pedal note.
Pedal notes should be notated below the two staves in a rhythmic notation where a pedal symbol replaces a note head. A verbal explanation is necessary.