There are several places. Submittable is a great resource. Many publishers and magazines use it to receive submissions. You could also try websites like Wattpad, although it's more about building an audience first and potentially getting noticed by publishers or agents from there. Some independent publishers might be interested too. Just look for ones that accept short story submissions.
You could try selling them on popular online writing platforms like Wattpad or Kindle Direct Publishing. They have a wide reach and can expose your work to a large audience.
Some literary magazines and anthologies also accept submissions for short stories. You could look for those that match your genre and style. For example, 'The New Yorker' or 'Clarkesworld Magazine'.
There are specialized short - story markets. For example, some small presses focus specifically on short stories. You can research and submit your stories to these small presses. Also, there are websites like Wattpad where you can gain a following for your short stories. If your stories are popular enough on Wattpad, it might attract the attention of publishers or agents who could then help you sell them.
Literary agents can be a great resource. If they like your short stories, they can help you find publishers who might be interested in buying the rights to your stories. You can find literary agents through online directories or by attending book fairs. Also, some local bookstores might be interested in stocking and selling self - published short story collections if you approach them in the right way.