How to tuck

From estrogen.fyi

Tucking involves hiding the appearance of your bulge for the purpose of wearing tight fitting dresses, trousers and other garments.

In order to effectively tuck and create a smooth surface in the front pelvis you need to use your hands to slowly push and slide up your testicles into the inguinal canal openings from below your torso. After moving them out of the way, fold your penis down towards your perineum to prevent them from falling back down and keep it flat with the contour of your crotch. Once it is in place you need to use something to secure it in such as tape (medical or sports tape should work), shapewear or tight underwear, or a gaff which is special tucking undergarments which you can buy online, in specialty trans/sex shops, or make your own simple version at home.

Tucking in Inguinal Canal