Bring the roller to a tire so it just touches the tire.
Make sure that the tire has been inflated to max. sidewall pressure. Slick, no thread narrow tires (23C) are the best to use on any trainer.
Tighten knob 2 complete revolutions.
That should do it. It is normal to hear and feel a slipping sound upon start up. But you should not hear it once the freewheel is up to speed. If you attempt large sudden changes in speed you will also get slippage.
The gears should be adequate to provide all of the resistance you need, unless you are Lance. In which case you can increase the resistance by holding the flywheel and tightening the bolt that holds it to the rollers. The factory set bolt tension is fine for 99% of us mere mortals. If you bought the unit used, maybe the previous person messed with it.
The black on the rollers is from tire slippage. You should not see a whole lot of it. Make sure you are at max pressure. and you did two complete knob revolutions.
There is a tire that conti makes that is only for home trainers that will not leave rubber and is excellent for preventing tire slippage and saving your tires:
You can't use it on the road, so if you do a lot of trainer and road workouts it's not worth the hassle of changing the tire. Some folks just use a spare wheel when they are on trainers.
Can't help you on the "pedal slap" since I don't know what you mean - unless you are referring to the slippage.