I agree with those who say walking alone will not do it, you have to combine it with healthier eating.
I am fortunate at 62 to not have any leg/knee issues, so I walk as much as I can, as fast as I can (I aim for a mile in 17 minutes or less). I have a fitbit, and 10K/steps a day I consider a bare minimum. I can easily do over 20K by adding activities such as golfing (where I walk the 18 hole course and use the push cart in a way to also get some upper body exercise in) or using a push mower. The gym is open again and very lightly attended, which makes it easy to stop in for an elliptical workout. COVID 19 shopping also helped, parking far away and walking in the large stores.
For diet, the biggest thing I watch is added sugar. I have a sweet tooth but I keep well below the daily sugar guidelines, which one can meet with just a single can of soda. I have stopped drinking sugared soda completely. I do drink the zero sugar soda, it tastes fine to me and better than the diet soda. I make pitchers of Arnold Palmer (ice tea and lemonade) using Erythritol - the one sweetener to me that tastes most like sugar but without any aftertaste. I try to snack as much as possible on fruits (my favorites being oranges, pineapples, strawberries, and bananas); I make my own smoothies with low sugar Gatorade, protein powder, and a mix of the above fruits than keep me from snacking for hours).
I'm not perfect, but I have cut way back on carbs. Instead of finishing off a large bag of chips in a single sitting, I will eat a small bowl of chips once a day. Instead of eating a 16 ounce bag of M&M peanuts several times a week, I'll eat a ounce every couple of days. I will also snack on dark chocolate and yogurt than has 5 grams or less of added sugar. Once a month I will treat myself to cookies. However, I do this snacking keeping an eye on the sugar intake guidelines, as well as how many calories I am burning in a day.
Spring through Fall I have more of a problem keeping weight on. It is winter that I need to pay attention to, and during winter I am much stricter with my diet and more regimented with my workouts.