If you know the PL/DPL tone, you need to program it when you enter the frequency. If you don't have the tone for a specific frequency, you can program the scanner to detect the tone for you. After you program the frequency and set the Audio Type to Analog, set CTCSS/DSC to Search and when the frequency is active, the tone will flash on the display. Be aware that if one or more agencies that use the same frequency are within receiving range of your scanner it it will detect those tones also. After you get the correct tone for the frequency, you can go back and program it. Just be sure your hearing the agency you want to listen to, and not another one, before you verify and program the tone.
As for digital frequencies, they don't use PL/DPL. They use NAC which works the same way as PL/DPL.
The 996T will not detect NAC tones. The scanner doesn't have that capability. The 996XT does.