In plain words
The one reality that is Om parted into three and became ahaṅkāra, and of that ahaṅkāra it is itself the witness. To awaken this knowing You stood among us as the supreme ācārya. Hari, salutation to Nārāyaṇa.
Word for word
The reality that is Oṃkāra, parting at once into three, is itself the witness of that which became the ahaṅkāra; O You in the form of the supreme ācārya, who stood as the one to bring that awareness! Hari, salutation to Nārāyaṇa.