Or you can buy compression boxers.
Consider source before you follow advice.
You should try the Andrew Christian Trophy Boy collection. It is specially designed for guys with a larger package. The underwear is available as a boxer, brief or jock and in various different designs. The underwear is fitted but has a large front pouch which you won't fall out of. The front pouch gives you extra space so you are not squashed, hot and sweaty. It allows you to naturally hang free. It feels a bit strange at first but you should soon notice that it is much more comfortable.