I am sorry, I was not sure what you meant when you said "you have plugged the screenshot to your computer"!!
There are 2 other easy ways to attach the screenshot.... 1) Open the King Community page on your phone itself and log-in --> Click on "Attach Image" icon and select "Choose Files" --> A window will pop up for you to choose from your Gallery --> Select the pic.
2) Send the screenshot to your email --> Open your email and download the picture to your computer --> Now, "Choose Files" option from Attach Image icon --> Go to "Downloads" folder and select the screenshot.
Please let me know if you need further assistance. Have a great rest of the weekend!