You don't need a gym to do weight training; but you do need a proper understanding of human anatomy, fitness and resistance exercise.
Lifting weights is not a matter of more is better. People who start lifting weights will often do too much and cause damage; but if you start with what is relatively easy; and build your strength slowly, lifting with the right number of repetitions and moving properly when you lift - then there is no reason you cannot build your strength with weight training at home.
