Yagya means unwinding the spiritual knots through mentation or japa one do (with or even without physical fire rituals).
The internal mental activation shall activate various spiritual knot (chakras, latayaf) of human embryological neuro- dermatological and brain units.
These knots are various human body areas ( ksetras) including Shudra, Vaish, Shatriya, Brahmin; Brikuti ( front third eye); Trikuti ( third eye at back); Sahastradhara ; Khechari kriya; Brahamrander ( heart) yagya leading to Sashupti (kshar Brahm) , Sarvikalp Samadhi ( Akshar Brahm), Nirvikalp samadhi ( PRA Brahm) and finally Nishkaam Karm yagya before death and now becoming capable of transmitting Pratpar praksh from own ❤️ heart to another ❤️ heart thereby called Gyani or the experienced. This Gyani continue to live in Hari dham after death and achieves Nirvana.
chapter 4 verse 24, 25,26,27, 28,29,30,31,32,33,34.
There fore either do long procedures of Yagya or visit one Gyani.