Teaching with Moodle

Hello RabNawaz and welcome here from the recently completed Learn Moodle MOOC. I have split your question from the previous thread so we can start a new discussion.  I'm not entirely sure why you want to add files to a category - I presume you mean a category page where the courses are listed? Such as https://demo.moodle.net/course/index.php?categoryid=1 ? If so, and you definitely know why you want to upload files to a category page,  then.....

 click "Edit this category" and make sure you have got it set to HTML (in the bottom at the dropdown menu) and then you can upload files by typing in text in the text box, selecting the words and then clicking the link icon and browsing to upload a file.