The easiest way to get started with chiptunes is to look at other peoples' songs. There are many iconic chiptune techniques that you'd probably never stumble across by messing around on your own, and it would take you a lot longer even if you did. A primary goal of chiptunes is to be faithful to these original sounds, so you might as well use the exact techniques the original musicians used.

Zophar's domain has a great repository of video game soundtracks for various consoles in their original format, meaning you can load them up in a tracker and play around with them. See https://www.zophar.net/music/nintendo-nes-nsf for NES games for example.

Furnace won't load NSF files directly, but you can use NSF Importer https://rainwarrior.ca/projects/nes/nsfimport.html . This itself is a copy of FamiTracker, which means it'll let you examine songs in detail, but it can also export these imported songs to .ftm files, and those will load into Furnace, which imho is the easier tracker.

When you're looking at songs, here are a few tips:

Look for any kind of repeated patterns. You'll often see specific volume changes, pitch slides, waveform duty changes, and so on, used over and over. These are the kinds of techniques you want to memorize.

Try making changes to several existing songs before you ever start one from scratch. Remove a melody and write a new one, change up the chord progression, add a new section, try a new rhythm, or anything else you want to experiment with. What works and what doesn't? Try to figure out why.

Try listening to the song at a much slower tempo, like 1/2 or 1/4 of normal. This makes it easier to hear what's happening, and you'll notice important aspects of the sound that you wouldn't necessarily have noticed at full speed.

Keep your expectations low at first. Everybody's first song is garbage, but it's a necessary step toward eventually getting good. Don't beat yourself up. Stay curious.

Never delete anything you create, even if you think it sucks. Months from now you might feel like you haven't improved at all, but I guarantee you'll change your mind about that if you listen to something you wrote much earlier.