I had an Anon request for “How to tuck, with pictures” while this might not be what they were hoping for, it may be helpful to some people.
Step 1: Above the base of your penis on both sides is a natural pocket that testes descend from. That is were they will be put while tucking. Gently press each testicle up their respective side until they pop into place above the penis. See 1 through 4 above.
If you have any trouble when you first try, laying down on your back or taking a warm bath/shower can help.
Step 2: Now that the jewels are put away (you may need use your finger to keep them there) gather the scrotal skin together with the penis as seen in 3 and 4 above
Step 3: Pull everything back towards your butt and press it up.
Step 4: Hold everything in place with your panties/shapewear/tights etc.
In some instances when you need a more secure hold you can use tape. However, that is a tricky process that varies from person to person, and I would not recommend it unless you really need to use it.