Every Yantra is active only when it has been energized. Yantras are associated with the five elements of the world and individual Gods and Goddesses. The ancient texts outline a 16 step invocation and pooja ceremony for the energization of Yantras.
The one who performs the invocation ceremony is called the "Sadhaka". He takes flowers in his hands and they are offered to the specific Deva or Devi the Yantra is associated with. The specific Deva or Devi is called the "Ishtadev or Ishta". The following steps are followed:
The first step is called Poorv Poojan where flowers are offered to the deity while reciting the Bija Mantra (specific mantra of the Yantra):
"Devaye Namah Aavahanam Samarpayam"
Then flowers are offered to the Aasana (The mat on which the Sadhaka is sitting) and the following mantra is recited:
"Devaya Namah Aasanam Samarpayami"
Water is offered to the deity as a symbol of washing their feet by saying:
"Devaye Paydam Samarpayami"
Three Achman (purification of the Sadhaka by sprinkling mantra infused water over himself) while reciting
"Devaye Aaradhye Samarpyami"
Bath is offered to the deity while reciting
"Devsya Asnanam Samarpayami"
Panch Amrit (a combination of five objects: milk, ghee, curd, honey, ganga jal) bath is offered to the deity with the mantra:
"Devaye Panchamritasnanam Samarpayami"
Then begins the Utter Pooja where mantras are recited for the clothes and Yagyopaveet thread (sacred white thread also called "Janeu") that the Sadhaka is wearing.
Gandh(Fragrance) is applied to the deity with
"Devaye Gandh Samarpyami"
Unbroken rice is offered with
"Devaye Akshtaan Samarpyami"
Flowers are offered with the recitation of
"Devaye Pushparni Samarpyami"
Dhoop (Incense) is lighted with the mantra
"Devaye Dhoopam Samarpyami"
Diya (Lamp) is lit and is offered to the deity with the mantra:
"Devaye Deepam Samarpyami"
Fruits are offered while reciting
"Devaye Naivedyam phalam cha Samrpyami"
Pan Supari (Betel leaf and nut) are offered with
"Devaye Tambulam Samarpyami"
For Aarti recite the mantra
"Devaye Pradakshirnam Samarpyami"
Pradakshina (to walk around the main deity and the Yantra) is done thrice with the recitation of this mantra.The pooja and invocation ceremony are finished by a final offering of the flowers and Namaskar with folded hands and with the final recitation of Bija Mantras with specific desires which need to be fulfilled.