How can I attach a picture in conversation window?

We have currently disabled this function
You can upload the image to imgur.com and get the image link

You can include image links in chat by selecting the insert image image icon and selecting the chain icon to insert image links.
or
You can get the bbcode image link from the imgur page and put it in the chat box (I recommend this method to help you put the image in faster)
We are fixing the Images.paperzonevn.com page (after completion, you can use this website to upload images to get the image link to put into chat as quickly as possible, and only use it for conversation)