How can I promote a published article?
There are plenty of options when it comes to promoting your work, both amongst fellow scientists and the general public.
The first and most obvious is giving talks about your work either within your own institution or at other universities. If you're really keen to do this, don't wait for an invitation to speak. It's ok to email the organiser of a department's seminar series and ask if they have any free slots in the next few months. Most seminar organisers I know are very grateful when someone volunteers to speak, as it makes their organisational job so much easier. One bonus of the pandemic is that everyone is giving talks online at the moment, so you can probably give more talks than usual and in locations that might normally be too expensive to travel to for one fifty minute seminar.
Related to this is speaking at conferences. The typical conference season is the summer, but again with everything being online at the moment, more and more conferences are happening at different times. Talking at an online conference is obviously not a good replica of meeting in person, where it's much easier to strike up casual conversation about your work in the queue for coffee, but it's better than nothing.
Furthermore, you can try using social media. In my field, it's quite common to write a Twitter thread explaining your results when you publish a new paper, so you could do something similar. This only works if most of your followers are fellow academics; if your only followers are friends from school or fellow football fans (for example), they may be less interested. Personally, I prefer to write a blog post about my work and then draw people's attention to the post on Twitter. A friend of mine makes Youtube videos. This is your chance to get creative!
Finally, if your work is sufficiently high-profile, you could get in touch with your university's press office and ask if they will write a press release for you. This is presumably a more difficult process to go through but is clearly an excellent way to promote your work to a much wider audience than just academics.