How do I go about this? Are there any free resources that’ll help me get started?
I see people advising to start with a small project, but you need to get some basics down right? What language? How to develop it and stuff?
My only experience is some very basic C programming classes I took during school.
Pick a language to start. If you want to automate CAD, maybe it has an existing scripting language built-in?
Learn the basics from the documentation. Look at the examples. Learn how to search for specific answers.
Finally, practice a lot. Most of the challenge is breaking a problem down into discrete steps (your algorithm), which can be written in pseudo-code. The implementation of that algorithm may look different depending on what the target language is, or what library/tools you can leverage within that language.
https://codingbat.com/ if you choose Java or Python
https://www.freecodecamp.org/
https://adventofcode.com/ has easy-to-challenging problems suitable for any language