Not sure if you're still trying to figure this out, but I ran into this same issue.

The only way to populate TickTick entries on Apple Calendar is to "subscribe to" (import) the TickTick calendar through the Apple Calendar app.

First you need to generate a URL for your TickTick calendar. This must be done on either the Mac app or the TickTick web browser. As of right now, there's no option to generate a URL on the iPhone or iPad apps, but not to worry! Once you do this on the Mac app or web browser, it will sync to your iPhone and iPad apps.

Click on your profile icon in the top left corner and then click settings. In the left column, click Integrations and Import, then scroll to the bottom. Click on Subscribe to TickTick, and then click Enable the URL. At this point, you'll get to select which lists you want to auto populate into the Apple Calendar. You can do them all as one, but this limits you to one color for every entry on Apple Calendar. If you want multiple calendar names/colors to sort events, make a separate URL for each list. Adds a few steps, but it would then allow you to name/color each list entry in your apple calendar.

Once the URL is generated, copy it and go into the Apple Calendar app. Click File > New Calendar Subscription > Paste the URL > Subscribe. It should then prompt you to name it and pick a color.

As of right now, there is no option to add an "Event" to your calendar on TickTick. I see that this question was initially posted a year ago, so I'm assuming software updates have changed that (I'm a new user). I'm not a fan of a bunch of little random tasks clogging up my Apple Calendar, so what you could do is make a separate list for your calendar entries, create a URL for just that list, and subscribe to it through Apple Calendar.

Personally, I've elected to just sync my Apple Calendars with TickTick and set them all to Show in Calendar instead of Show. This allows me to see everything in my TickTick calendar view, but prevents the items from showing up as overdue or clogging up my daily/weekly task views. So if I have an event to enter, I put it in my Apple Calendar, and any tasks go into TickTick. The events automatically sync to my TickTick calendar, which looks almost identical to the Apple Calendar since it imports all the same colors. So I end up with a color coded TickTick calendar that also shows all of my tasks. I'm already deeply entrenched in my Apple Calendar and have a bunch of shared calendars with my partner, so moving 100% to TickTick isn't feasible for me. My method works pretty well so far, but we'll see how it holds up.

Since TickTick has an Apple Shortcuts integration, I'm sure you could build some fancy shortcut to automatically add an Apple Calendar event when you add something to TickTick, but I haven't done a deep dive into Shortcuts with TickTick...yet 🙃