The thing is that i dont know where to start, is there any tutorial for dynamic bones or constraints? i have no idea its so confusing
The easiest method is to add in a penis object with dynamic bones. Penis7 is usually the go-to as it has the most dynamic bones available. From there, position these in the correct spots on the characters and then parent them to the "Penis" subsection. After this, left click on the KKPE button and then click "options". Adjust "adv mode height" and "adv mode width" so the sliders are a bit larger than their defaults.
Next, add a dynamic bone collider to the scene. You'll want to move this to the spot you want to target the dick to, and parent it to the character or object appropriately.
Select the bone collider, then right click the KKPE icon to open the bone collider editor. Configure the bone collder to "all off", and set it to "inside". Now, you can scroll through the available bones in the bone collider editor. This will show you EVERY dynamic bone in the scene, so that's things like hair, skirts, clothing items, BetterPenetration bones, etc. We adjusted the adv mode height and width earlier because otherwise this window is too damn small to work with.
Scroll through until you see your penis7 object, and select Penis00, Penis01, Penis03, Penis02, and Penis01. These are the most frequently used bones, but certain orientations of the penis object and desired "angle of attack" may require you to noodle around with which bones to use for your particular use case. Whatever you bubble in is going to be a bone effected by that particular collider. After all of this, you will have to tweak the height, radius, position, and rotation of the bone collider to fine-tune the penetration so it looks right or is actually hitting the right spot.
It sounds complicated but it really isn't that difficult. It becomes tedious when you are dealing with more than one dick and more than one bone collider, as you have to keep track of which collider is for which penis object.