Your question isn't very clear, perhaps an example would help. As OriginalGriff stated, if there's no relation between the tables, you cannot 'navigate' in the data.
However if you want to create all combinations of students and courses, you could create a cartesian product between them. For example:
var all = from student in FirstTable.AsEnumerable()
from course in SecondTable.AsEnumerable()
select {
student.Id,
student.Name,
course.NameOfCourse,
course.NumOfCourse
}
This should contain all the combinations and you can put the results into a new datatable.