If you gave your students an assignment outside of the online course platform and want to have the grade for the assignment added into the online gradebook for easier grade calculation, you can set up an assignment page to accomplish this.
Start by creating a new assignment-type page by following the instructions found here. For the "Submission Type", choose the "On Paper" option. You will want to use the "Checklist for Creating Content" to make sure you have the grading weight, etc., set up correctly.
Once the assignment page has been created, it will now show in your gradebook so you can manually enter the students' grades.