Fusion 360 is a 3D CAD, CAM, and CAE tool from Autodesk that connects your entire product development process in a single cloud-based platform that works on both Mac and PC.
It is free to use for hobbyists and startups generating <$100k/year in total revenue. See this web page on the Autodesk site for further details.
There are several very good tutorials on YouTube. Here are a couple that will give you a good start…
Lars Christensen posts regular YouTube videos on various aspects of Fusion 360. They are pitched at all levels and include many basic guides on how make best use of the software. You can find his videos here on YouTube.
large:A5bc9c3S12g
Paul McWhorter is an ex-maths teacher whose individual teaching style will lead you through the design process.
large:y5tp4QXciK4