Bhattathri in this Sloka outlines the process of liberation (salvation) from the higher Lokas for the Krama Mukti Sadakas who have reached there and living there.
The yogi who attains this aspect of the migration into the Brahmaloka or in Thy abode, Vaikuntha is liberated at the time of Maha Pralaya. Or, if he so desires, he is liberated even earlier by piercing through the Brahmaanda and releasing himself by his yogic power.
Meaning of the Sanskrit Words
तत्र वा - either there (in Brahmaloka)
तव पदे-अथवा - or in Thy world (Vaikuntha)
वसन् - residing
प्राकृतप्रलये - at the time of Prakrita pralaya
एति मुक्तताम् - he attains liberation
स्वेच्छया खलु पुरा - (or) at his will even earlier, indeed