It depends on the instance. Your account is on lemm.ee, and in the sidebar of lemm.ee it says that you need to wait 4 weeks.

In the meantime, you can still link to image files directly.

If you have a link to the image file:

• Posts: paste it info the URL field
• Comments or the post body: use the ![optional description](URL) format

For example: ![two floating sea otters](https://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Sea_Otters.jpg/320px-Sea_Otters.jpg)

If you don't have a link to the image, you can upload to Imgur or something like catbox.moe

Some instances don't allow it at all, so it's sometimes best to upload elsewhere and embed the picture with this syntax: