Hi sukhdeep,
The yantras you need to keep in your pooja place and every day perform pooja as usual you do it for your lord. Place your right had ring finger on the center part of the cube and the chant the specfici mantras prescribed to you for saturn, rahu and ketu respectively. The next time when you are going out related to your work is concerned take out the ketu yantra offer it respect and chant the mantra of ketu for 7 times minimum and fold keep it in your pocket. along with 33 yantra.
And other yantra’s use will let you know later.
GOD BLESS!!!
Srinivasa Temkar