simplest possible teaching on the four Satipatthana I have read about


  The Satipatthana Sutta, the Discourse on the Foundations of
  Mindfulness, is generally regarded as the canonical Buddhist text with
  the fullest instructions on the system of meditation unique to the Buddha's own dispensation. 


there is four types 


Cittanupassana
Vedananupassana
Dhammanupassana
Kayanupassana


https://www.accesstoinsight.org/lib/authors/soma/wayof.html
https://www.accesstoinsight.org/tipitaka/dn/dn.22.0.than.html

Can anyone give clarification in simple words?
I want some clarification on how to start and how to do it.
One of the simplest renderings of the 4 Foundations of Mindfulness is:


  
And what, bhikshus, is right mindfulness?
Here, bhikshus, 
a monk dwells  exertive, clearly knowing, mindful, observing the body in the body, 
   removing covetousness and displeasure in the world;
a monk dwells exertive, clearly knowing, mindful, observing feelings in the feelings, 
   removing covetousness and displeasure in the world;
a monk dwells exertive, clearly knowing, mindful, observing the mind in the mind, 
   removing covetousness and displeasure in the world; 
a monk dwells exertive, clearly knowing, mindful, observing dharmas in the dharmas, 
   removing covetousness and displeasure in the world.
This, bhikshus, is called right mindfulness.

  


(Magga) Vibhaṅga Sutta similar passage in Sacca Vibhanga Sutta

"removing covetousness and displeasure in the world" means you are to be equanimous without getting attached to the pleasant or averse to the unpleasant. You have to see impermanence also to remove ignorance.