This verse is from the Bhagavad Gita, Chapter 6, Verse 12. It is written in Sanskrit and translates to English as follows:
tatraikāgraṁ manaḥ kṛitvā yata-chittendriya-kriyaḥ
upaviśhyāsane yuñjyād yogam ātma-viśhuddhaye || 12 ||
"Fixing the mind at that one point, controlling the activities of the mind and senses, one should practice yoga with the aim of self-purification, sitting on the seat (asana)."
tatra: in that place
ekāgraṁ: by establishing concentration (meditation)
mana: kṛtvā: by controlling
yatachittendriyakriya: by controlling the actions of the mind and senses
āsane: by sitting on a seat
upaviśhyāsane: by connecting
yunjyāt: by connecting Yogam: Yoga for the purification of the soul.