If you don't have the mobility or endurance, exercising a few minutes several times a day is good. Walking, swimming and water aerobics are healthy low-impact exercises.
Strength training, perform one to two sets of 10 to 15 repetitions of weight bearing exercises two to three times a week. If you don't have dumb bells then use resistance bands or machines. You can perform pushups against a wall and squats by sitting in a chair and then standing.
You could join a yoga class.