Age does not close the door
Older adults can improve strength through resistance training. A Cochrane review combined 121 trials involving 6,700 participants and found gains in strength, with improvements in some everyday physical tasks too.
Resistance means something your muscles work against. That might be your body weight, a resistance band, a machine or a dumbbell. A gym is one option, not an entry requirement.
A useful reason to begin
Think about an activity you would like to feel more capable doing: getting out of a chair, carrying shopping or continuing a favourite hobby. That gives learning the movements a purpose beyond a number on a weight.
What this does not promise
The Cochrane review is from 2009, and its trials did not report possible harms consistently. The 2019 NSCA position statement adds guidance for older adults, including people with chronic conditions. Neither source establishes that a free website will reproduce a supervised training program's results.
People differ in experience, balance, health and support needs. If you are unsure what suits you, a qualified exercise or healthcare professional can help you choose a starting point.