Have you ever made extra parts or replaced things on a model kit?
Have you worked with styrene, acrylic, wood, metal, from basic blocks?
The normal progression of skills is starting small and continually making bigger and more complex things over time. Fixing mistakes and learning new techniques, and honing your skills so that you can get to a point where you can make a whole complex item without getting frustrated and giving up.
Gaining this experience also helps you figure out what materials and techniques will work best for the subject you want to build. It also helps you decipher plans and photos to determine how best to break down the subject into build able sections.
As far as subjects go, a barge is probably the simplest thing you could start on, then any small modern tug with flat surfaces. Then try an older tug with more curves.
One of the ways to judge the skills of a chef is how they cook a scrambled egg. Meaning you have to master the basics before you can move on to bigger and better things.
I'm not trying to discourage you, but it will be impossible to tell you everything you will need to know to accomplish your goal on your first try. Start small and take it one step at a time. Reach out for help on specific steps you get stuck on.
Look through build articles on model warships or warship models underway. Or any of the other Facebook or online forum groups out there.