Housing, codice fiscale and money

Housing: ask the PhD office and the department first; they often know rooms and residences that take doctoral students. Book a refundable 30 day stay for arrival. Ask for a registered contract (contratto registrato) for any long term room, and never pay before seeing the room, at least by video, with a real contract. Rents by city are in the rent table.
Codice fiscale: your Italian tax code, free, needed for the scholarship payments, bank, SIM and rent. Get it at an Agenzia delle Entrate office, through the university's welcome desk, or ask your embassy whether it issues one before travel.
Bank account: the scholarship is paid into an Italian account in your name, so open one in your first weeks. Some banks ask for the permit receipt.
First payment: payment dates are set by each university (P18), and the first payment can come some weeks after you enrol. Arrive with money for at least two months.
From Bangladesh: move money only through official banking channels and keep receipts.

This page explains official rules in plain language. I am not an immigration adviser and I do not give visa advice. For that, always use official government sources. Rules change: confirm with your university, the embassy and VFS before you act.