If by manhood, you're referring to the size of your penis, then let's be honest and say it outright here that you cannot possible add more girth and length to it except if you pay some hotshot doctor to butcher you.
Yes, surgery is the only proven method to increase penile size.
But even surgery has gained not-so-good reputation as there have been reports that many men who decided to go through it have been experiencing erection problems.
Just like most men, you're probably asking yourself, "How to increase my manhood?" Well, you cannot add any more dimensions to it but there are ways to improve it how it looks and how it stands when fully erected.
The idea here is to improve blood flow all the way to its head because the more blood being pumped into it, the bigger your tool will be.
First off, you must lose belly fat if you want your member to achieve its full potential.
Too much fat in this section will make your penis "shrink" amidst the sea of fat hanging around.
So you must make an effort to exercise regularly in order to trim down unwanted fats in this region.
By engaging on sports and doing sit-ups on a regular basis, you're doing yourself a big favor.
Another answer to your How to increase my manhood question is to increase your sexual prowess in bed and not the size of your tool.
This means learning more about the tricks of playing around a woman's vagina, making her scream on top of her lungs, and making her lose her mind during the intercourse.