I was in the same position as you were about 6 months ago. I started HTB knowing only the very basics of Linux, so not exactly from zero knowledge, but pretty close to nothing. HTB isn’t a super great place to start out, but here’s how I did it. To learn the very basics I watched some of Hackersploit’s videos about the basics of Linux, nmap, metasploit and a few other tools. I also watched some videos about basic networking concepts and learned the very basics of python scripting. After I felt like I understood enough to attempt my first box, I picked the easiest machine on HTB and just went at it. I failed miserably, didn’t even root it, and that was with a lot of hand-holding too. But I kept attempting more boxes, and I got better over time. In the beginning, I did rely a lot on the amazing, and very helpful discord community, and I found that for me that was the best way to learn. So my advice to you is to just start, and if you’re stuck, google is your best friend, and if you don’t know what to google, ask for help.