what training do i need to walk a half marathon

The First 3 Weeks: Are for easing you into a regular walking schedule, helping you to make it a part of your daily life. Therefore we won’t be building mileage in the first 3 weeks. For those of you who are regular walkers (those who walk 30 minutes at least 3 times a week) may skip the first 3-4 weeks and make it a 12 week program.
Weeks 4 - 16:
One walk during the week is based off of time in minutes (20’-50’) instead of mileage. This is to take the focus off of how many miles you are going. If you want then of course you will be able to estimate how far you walk based off of how many miles you can walk per hour. The 3 other scheduled walks for the week work on building your mileage and helping your body adjust to walking farther and farther. Cross Training (XT) is incorporated into the program to work out your other non-running muscles, keeping them strong and flexible. Your cross training should involve an aerobic activity (swimming, cycling, skiing, etc.) or some sort of strength training program. If you opt for strength training though don’t make it too strenuous. You can follow this beginner strength plan.
Your Pace during the week should be easy. You should be able to hold a conversation with a friend. As a beginner you don’t want to push hard through every training walk that you do as that can set you up for injury. Therefore do 2 of your walks during the week at an easy pace, and one at a slightly harder pace. Your long walk of the week (on the weekends) should be at a comfortable pace. The idea of this walk is to build up your endurance and mimic race day situations so use them as a mock run.