Can anyone explain to me how that is done? I registered at EDSM before DW started but couldn't figure out how it works so I never used it. As a result I show up as 0% progress.
Once you've registered with EDSM you need to upload your progress to the site.
The first step is to enable verbose logging in your game - there are instructions repeated all over the place on how to do this, but
this thread has them and may become additionally relevant in a minute.
Now you've got the game logging the systems you visit you can upload them to EDSM.
You can run a 3rd party application like ED Discovery (that thread I just linked) which is very nice (and I'm not just saying that because I'm one of the developers working on it - although the lion's share of the credit goes to CMDR Finwen). That lets you sync your travel history with EDSM by clicking a button once you've done a bit of config so it knows about your EDSM account (and also gives you an UI for trilateration and plotting your journey on an assortment of galaxy maps.
Alternative, you can just load the logs straight into EDSM
here but that's a bit more faff (IMO).
Then EDSM will know where you are.
You could leave the logging off and just enter your system into the 'Where are you?' text box at the top of the EDSM front page after every jump, or after selected jumps and I think that would probably work so long as you're logged in, but that's the most labour intensive option of all.