To enter the stream of Noble Eightfold Path, that is, to attain Sotāpanna (often called Stream Enterer), there are four conditions. See, Sotāpattiphala Sutta (SN 55.55) and Dutiya Sāriputta Sutta (SN 55.5).
The four requirements for someone to attain the Stāpanna stage of Nibbāna are as stated: “Cattārome, bhikkhave, dhammā bhāvitā bahulīkatā sotāpattiphalasacchikiriyāya saṃvattanti. Katame cattāro? Sappurisasaṃsevo, saddhammassavanaṃ, yonisomanasikāro, dhammānudhammappaṭipatti ”.
First condition: sappurisasaṃsevo = sappurisa + saṃsevo = noble person + associating = associating with a noble person. This noble person has been wrongly mistaken as kalyāna mittā referring to good friend but should be good noble friend.
Second condition: saddhammassavana = saddhamma + savana = true dhamma + hearing = hearing the true dhamma (with correct meaning for some concepts, example anicca, dukkha, and anattā) from the associated noble person. While reading (the true dhamma) is enough to get to the Sotāpanna Anugāmi (or Cūḷa Sotāpanna) stage (path/magga), hearing is necessary to attain the Sotāpanna stage (fruition/phala).
Third condition: act with yonisomanasikāro = yoni + so + manasikāro = origin + oneself + with this in mind = act with the origin [refers to origin of bhava (existence) and origin of jāti (birth)] of oneself in mind (meaning understanding and follow the process of Paṭicca Samuppāda [those twelve factors lead to whole mass of suffering, with understanding of true dhamma, slowly stop these twelve factors from arising and end suffering!] with the understanding from Second condition of true dhamma).
Fourth condition: dhammānudhammappaṭipatti = dhamma + anu + Dhamma + paṭipatti = true dhamma one follows + according to + Buddha Dhamma + practice, or ‘pursuance’ of the teaching = practice the true dhamma one follows according to the Buddha Dhamma. There is a series of four suttā, starting with the Anudhamma Sutta (SN 22.39).