How to get 3d Models
There are two primary ways to get 3d models for you to print. You can either make them yourself using a C.A.D. (Computer aided design) software or you can source them from a free repository on the internet. When it comes to sourcing 3d models off the internet there is thousands and thousands of models available for free on platforms like Thingiverse and Thangs. On these platforms you can generally find lots of cool trinkets or specific parts for a generally used product. However, these sites most likely would not have anything for you if you were trying to make something cool that's specific to your life. For example, if you were trying to find a mounting design for a specific motor or to make a stand for a souvenir you most likely wouldn't be able to find anything. This then leaves you with the option of creating a model yourself.
When it comes to 3d modeling there are thousands of different softwares available which each have their own quirks. I primarily use Autodesk Inventor Professional but I've also heard good things about another program called OnShape As a warning about Autodesk, I have free access to autodesk as I am a student but if you are not currently enrolled in an academic institution or other that provides Autodesk for free it is really expensive. If you can get Autodesk for free I recommend it, if not, I would use OnShape. Now, once you actually have a software I recommend using youtube tutorials or similar to help you become familiar with all the tools of Autodesk. Additionally, I found a fun exercise to be to recreate objects around my room as a way of developing my CAD skills. Once you've designed something you want to print you then have to move onto the final step, initiating the 3d print.