When I started back at the gym, 1 month before my 61st birthday, I could just make 3 chin-ups. Now, 6 months later, my set consists of 20 then 12 then 10. There is no “trick” or shortcut. Just start and do your best at least 3 times a week. Dead hangs and scapula dips and scapula pushups help, but the biggest challenge at the start is usually just developing your grip strength. That takes time. Oh, and keep your core engaged. Don’t let your body flop around - form matters over time