Here is a simple, traditional outline for the Fourth Day (Upadhyaya Pad) of Navpad Oli Ayambil:

• Day/Pad: This is the 4th Pad in Navpad Oli, called Upadhyaya Pad. The focus is on the teacher-priest aspect and the learning/teaching role in the sangha. In practice, Ayambil is kept with very plain food and devotional acts. ( jainknowledge.com)
• Food for the day: Eat boiled mung beans (moong). The preparation is plain, without taste-enhancers like oil. This day’s Ayambil uses mung as the chosen grain. ( jainknowledge.com)
• Other practices: Along with the meal, the day typically includes Navpad/Navachakra aradhana, along with standard Navpad Oli observances (prayer, reflection, and proper conduct). Details can vary by local sangh, but the core is the Upadhyaya Pad focus and the single plain meal. ( jainknowledge.com)
• Notes on tradition: There can be slight differences between Digambar and Shwetambar practices in liturgy or exact sequence, but both traditions honor the Upadhyaya Pad and the same spirit of Ayambil (detachment from taste, discipline, devotion). ( vitraagjainsangh.org)

You can read more here and related Navpad Oli notes.