Click on Solutions-->goto IT knowledgebase--->
If you want to create a folder inside the IT Knowledgease, click on drop down "+New Article" at extreme top right--> it expands and says "New Folder" or "New Category"
If you want to create an article inside the folder or IT knowledgebase directly, click on +New Article.
Give the title or subject
Then give the description.---> Publish