I'd recommend
these morphs by
@WeebUVR. To use them it's pretty simple, just go to your Morphs section of your male character and search for the body part you want to adjust. Try "penis" or "genital" and several options appear.
For textures, I think it's a little bit harder to find standalone texture resources for male characters, but there're several CC-BY looks with custom textures that you could build upon. Use the search bar and look for resources with the "male" tag in the free looks category, you'll see several options. If you're looking exclusively for penis textures, WeebUVR
normal maps, and
@Jackaroo genital veins and
build a cock are some options.