Basically anything that lets you upload images can work. You could even use social media (in case they are set to public) like facebook, instagram, x (twitter), etc and paste the link to the images/post here. But it is not ideal.
You could also use free cloud services like Dropbox, Google Drive etc to upload images to. If you are uploading from your smartphone, there are free services that work via an app, like "Mega" among others.
For image upload services that work from your computer, there are a few. I personally use
www.directupload.eu but it is in German. There are others, like
www.freeimage.host or Imgur.com.
Or just google "free image upload service" and pick one that seems to be clear enough to understand.
The thing is that all these services have their own interface so you would need to figure out how to upload them and retrieve the image link afterwards on your own. But the concept is the same, you upload your images to the service's server and copy the URL (link) from the file's location which you then paste here.
EDIT, ok, you figured it out. I was too slow.