as N1GAW mentions, confirm them in use within your monitoring range first. [You did this and keep searching too]
then, enter them, as conventional channels.
Igonore the topic of ENC vs CLR for now, the big issue are they known in your area, and do keep searching as what is
dead quiet today, may become very active later [hours, days, weeks, months or even years]
Many of us, do tend to use AUTO vs locking in a PL/DPL/NAC [YMMV] as in my area we have a couple of frequencies used by
different agencies. One we have the VA Hosp using Analog [PL] and a DHS Agency using P25 [NAC] - yes same exact freq
you could [again your choice] program them individually [duplicate] one as Analog the other as P25
you may also need to do this to block out any interference from local sources [couple of mine get cable tv]
Before we rule them out as encrypted let's rule them in as being used. I have several encrypted freqs listed for the tracking of RIDs and NACs and occasionally hear clear traffic on fulltime encrypted channels.