Hello
@meye1099 and welcome. The planning stage is half of the fun!
My advice would be to start with two websites,
Pilgrims to Rome is a registered charity that aims to encourage and inform those making a pilgrimage to Rome along the Via Francigena.
pilgrimstorome.org.uk
The Via Francigena is one of the oldest and most popular pilgrim itineraries in Europe. With its 3200km from Canterbury to Rome and onwards to Santa Maria di Leuca in Southern Italy, it crosses 5 different European countries.
www.viefrancigene.org
and then ask more specific questions for clarification on this forum, where you will find a wealth of useful and friendly advice.
Where you start largely depends on how much time you have, and if you want to finish in Rome. People walk from Canterbury to Rome in 70-100 days (I took 87 including 5 rest days) and about half of that would be in Italy if you started at the Great St Bernard Pass. It obviously depends on how fast you walk
. People start from GSB from Aosta, and from all points south really. Siena and Lucca are popular places. There is no particularly recognised special place to start from.
The book by Roberta Ferraris, from Terre de Mezzo is useful, and is in English, and quite up to date. You can also download it as an app
from the publishers website from the app store of your phone. Search for <i percorsi di Terre di Mezzo>
https://www.amazon.co.uk/dp/8861894917/?tag=casaivar-21
Do come back here with more questions!! Tim