Need help in interpreting this

[RedFox]

Hello all - I am confused about how I interpret these verses form the 6th canto of the Srimad Bhagavatam. These are from the Narayana Kavacha. 

...kṛta-svāṅga-kara-nyāso mantrābhyāṁ vāg-yataḥ śuciḥ
nārāyaṇa-paraṁ varma sannahyed bhaya āgate
pādayor jānunor ūrvor udare hṛdy athorasi
mukhe śirasy ānupūrvyād oṁkārādīni vinyaset
oṁ namo nārāyaṇāyeti viparyayam athāpi vā

So here, should 'oṁkārādīni' be interpreted as 'preceding with the omkara', or 'begininng with the omkara' in the nyasa? 

Same goes with this one - 

kara-nyāsaṁ tataḥ kuryād dvādaśākṣara-vidyayā
praṇavādi-ya-kārāntam aṅguly-aṅguṣṭha-parvasu

'praṇavādi-ya-kārāntam' is 'starting the the pranava and ending with the 'ya' syllable'. 

So should the previous one also be interpreted that way? (ie Placing each syllable of oṁ namo nārāyaṇā in the places mentioned (om, na, mo etc.)? Or should each syllable of the mantra be preceded by om, and then be placed (om om, om na, om mo etc.)?

It has been interpreted differently in different places - seeking final clarity on this.