Geez! Besides normal activity, walk an extra mile every day for a couple of weeks. Then bump that to two miles a day. After a couple weeks of that, start bumping that up what you walk on weekends and maybe pick up your pace gradually. If that's too aggressive, start at half a mile a day and work your way up from there. Then, on Thanksgiving morning, walk a turkey trot 5K (3.11 miles). Those are usually family-oriented events, so a slow finish time - >1 hour - won't matter, especially if there's also a 10K distance.
Get to know trail systems in your area. As you gain endurance, work your way up to 5 or 6 miles on a weekend day (Hello! 10K = 6.22 miles!). Allow 6-12 months to get to the point where walking 4 or 5 or 6 miles on a single day is doable.
And carry and use a water bottle! Use sunscreen! And don't cheap out on shoes.