Bhashya
उपमन्त्रयते सकेत करोति, प्राथम्यात् स हिंकार ।ज्ञपयते तोषयति, स प्रस्ताव ।सहशयनम् एकपर्यङ्कगमनम्, सउद्गीथ , श्रेष्ठ्यात् ।प्रति स्त्रीं शयन स्त्रिया अभिमुखीभाव ,स प्रतिहार ।काल गच्छति मैथुनेन, पार समाप्तिं गच्छतितन्निधनम्, एतद्वामदेव्य मिथुने प्रोतम्, वाग्वम्बुमिथुनस-बन्धात् ॥
In plain words
The preliminary address with a sign is the hiṃkāra, because it comes first. The communication of desire and the giving of satisfaction is the prastāva. Lying together on a single bed is the udgītha, due to its pre-eminence. The woman turning to face her partner as they recline is the pratihāra. Time passing through intercourse and reaching its complete end is the nidhana. Thus the Vāmadevya chant is woven into sexual union, based on the underlying correspondence of speech and water.
Close to the Sanskrit
Addressing lovingly makes a sign, from priority that is the hiṃkāra. Makes known, satisfies, that is the prastāva. Lying together, going to a single couch, that is the udgītha, from pre-eminence. Towards the woman lying, the turning to face each other, that is the pratihāra. Time goes with sexual union, the completion goes to the end, that is the nidhana. This Vāmadevya is woven in the union, because of the connection of the speech-water pair.