How do I upload an image on the post?

[deviruzy 1]

 Good days to you.

 I noticed that people are using website called imgur to upload their images on their post. However, the image I uploaded from my imgur is not working here. It keeps telling me something like "This image extension is not allowed in this forum." I tried .png, .jpeg, .bmp. but all of them ended in same result. Can anyone tell me how to upload an image in Hercules post?

 Thank you.