This is because you do not have the required privilege for this. Please send a mail to web_intra@iitg.ac.in.
After login you should see a block in the left side of the page with title "Administration" under which you will see a link "Site Administration", click on "Site Administration" -> "Courses" -> "Manage courses and categories". Now click on desired "Course Categories" ( e.g. Biotechnology, Chemistry etc) and click on the "Create new course" link as shown in the picture below. If you do no see the "Manage courses and categories" link follow Q.2

This is becuase you have not enabled "self enrollment". First go to the course then go to Administration > Course administration > Users and click on "Enrolment methods" link. On the right hand side, a page will appear as shown in the picture below. If the "self enrollment" entry is not present add it using "Add method" dropdown menu. After adding click on the eye symbol as show in the picture below to enable the method. If you want to add an "Enrollment key" to the course see Q.6

All participants except the course creator ( which has the role Teacher ) has the default role of student inside a course. i.e. whoever enrolls for the course gets student role by default. The Teacher can assign roles explicitly.
By default all the users with any role can view and enroll for a course. If this is not desired, the course creator can set an "Enrollment key" for that course and provide the key to desired users. A "key" sign will appear for that course in the first page.
In a course, go to Administration > Course administration > Users > Enrolment methods and ensure the "eye" is opened for "self enrolment", then click the edit icon (gear symbol) on the right : Add your enrolment key in the box provided (Click Unmask to see what you are typing). Now save by clicking "save" button at the bottom of the page.
Please click on the "Turn editing on" button in the upper right corner of the page. You will see all the activity list.
Once any user enters the course, his role will be student by default ( It can be changed by the Teacher explicitly ).
A Student can't add any resource or activity in a course but can view it. For assignment activity he can upload assignments.
A "Non-editing Teacher" also can't add any resource or activity in a course but can view it. They can download the assignments submitted by the students and grade the assignments.
All users except the faculty members gets "Authenticated user" role after logging in. Authenticated users can't create anything. Once they enroll for a course, they become student for that course. ( see Q.2 )
If you are the creator of the course and have not unenrolled yorself from the course you have created, you can delete the course. Once you delete the course, it cann't be recovered. So you can just hide the course. Hidden courses are not visible for students. To Hide or Delete a course click Courses -> Add/edit courses -> Your Course Category. Then you will see an EYE symbol to hide/unhide and CROSS Symbol to delete the course.
If you are the creator of the course and want to allow another faculty to make modification on the course (Multiple faculties teaching one course). In a course, go to Administration > Course administration > Users > Enrolment methods. Now in the "Manual enrolments" click the icon "man with + sign". In the next page go to the right column "Not enrolled users" and search the email id in the search box. Click on the user appeared as a search result to select. Now select Teacher in the "Assign role" drop down menu and click on the "Add" button. That will add the user as a techer for the course.
You can tell the "Course Short Name" to the students, they will search it and will enrol it by themselves. You need to tell them the "Course Short Name" as well as the "Enrolment Key" that you have added at the time of creatin the course.


You can add students manually as shown in the image below.