This tutorial is for Siberian CMS Editor Image Uploader Module. You will find more details here: https://extensions.siberiancms.com/downloads/image-uploader-editor/
Go to https://api.imgur.com/#registerapp
Click on "register their application".
Fill details and click on Submit.
Now you will get Client ID. Copy-paste it in Backoffice >> Manage >> Modules >> Image Uploader