It is simple to enter exam results for a small number of students. Simply go to Students, find the relevant student, go to the Exams tab on their file and enter the result in the field set up for it.
However, If you have received a long list of exam results, it will be more convenient to enter them from the Exams list view.
Go to Student Activity > Exams.
That brings up a list of all exam entries.
If you use the Find function to restrict the list, and a Sort function to bring them into the same order as the list you have received, you can make entering the results as easy as possible.