Posh Dasmhi (Posha Dashami) is observed by some Jains as a fasting/discipline day in the Posha month. The exact vidhi (procedure) can vary between Digambar and Shwetambar traditions, and also from region to region. Here is a simple, traditional outline you can follow, keeping in mind the differences between traditions:

What is generally done (common elements)

• Upvas or partial fasting: Many observe a one-day vow (upvas) or a partial fast, often avoiding grains and certain foods, and consuming only light, non-sticky foods or liquids as permitted by one's tradition.
• Shramik/discipline day: Read or recite sadhana texts, reflect on conduct, and reduce activities not connected with spiritual practice.
• Samayik and/or Pratikraman: Perform a short Samayik (meditation on the four dharmas) and, if possible, Pratikraman (confession/reflection on wrongdoings) during the day.
• Puja/Aradhana: Offer prayers to the Tirthankaras, chant Namokar Mantra and other parikramas or stotras as prescribed by your guru or local lineage.
• Seva/ dana: Charity or helping others is encouraged, especially on observance days.
• Mokshan (mindfulness): Maintain strict awareness of non-violence and truth in thoughts, speech, and action.

Tradition-specific notes

• Digambar: The emphasis is often on rigorous vow and purity. Some Digambar practitioners may observe a stricter fast (no food or water for part or all of the day) and perform more intensive penance or meditation, within their personal capacity and guidance from a guru.
• Shwetambar: May include a lighter fast or a partial fast, with emphasis on sama-samaya (daily disciplines), Namokar recitation, and ritual yoga of internal purification. Some follow a vrata that allows certain fruits/dairy, depending on local practice.

Spiritual aim

• The core aim is to cultivate ahimsa (non-violence), satya (truth), and self-discipline, and to purify the mind through reduced external activity and focused sadhana on this auspicious day.

If you’d like, I can share more precise steps aligned with a specific tradition (Digambar or Shwetambar) or help you find a source in Jain scriptures or established Jain practice guides that detail Posh Dashmi observances for your lineage.