This question tends to be the first thing anyone new to rifing will ask. Rightfully so, you wish to ensure you take the proper steps out the gate.
There's a fundamental difference between killing and healing. In simplified terms, killing frequencies break a pathogen or parasite apart. Healing frequencies entrain rather than break.
Well, to keep things simple I will break it down even further here.
The simple answer is you can't make a mistake.
A frequency will resonate and do its job where needed, regardless of whether you think it's healing or killing.
If you are new to rifing and Spooky2, then the best way you can get started without trouble is to use the JW - Healing preset for everything -- yes even for killing.
This preset uses a square wave which is universal and capable of doing both healing and killing modalities well.
When you get further down the road, you will be in a position to decide when using JW - Killing may be more efficacious for the frequency sets you are targeting. JW - Killing uses a inverted sawtooth waveform which makes frequencies that resonate with pathogens particularly more effective, but may be too harsh for a frequency that resonates with your kidney.
So in summation, when starting out, use JW - Healing preset when trying out programs in Spooky2. As your knowledge and experience grows, feel free to explore more options.