You only need to create columns if you wish to return marks for submissions not handed in via Minerva.
Go to the Full Grade Centre and then select Create Column. (The Create Calculated Column is not for entering marks - use this if you need to do a calculation such as an average or total grade.)
Fill in the fields as relevant (you will need to enter a name and points possible). It is a good idea to give the item a category as otherwise other Grade Centre functions won't work properly e.g. Smart Views. Assignment and Test are the categories typically used.
Check the options, especially whether you want to show the column to students (relevant if the My Grades tool is used in your module). Click Submit when finished.
Now you should see the column in the Grade Centre and can either add marks directly into the cells or via a spreadsheet.
If you wish to make calculations using the Grade Centre, use the Create Calculated Column option. There are various choices: Average Column; Minimum/Maximum Column/Total Column and Weighted Column.
For all the calculated columns you can choose to make use of the categories function. If you want to do this, make sure you have read about categories first.
This will gave you the numeric average for the columns selected. You can select which columns to include or select via categories.
This will gave you the minimum/maximum grade for the columns selected. You can select which columns to include or select via categories.
This will add up columns/categories as selected. You can select which columns to include or select via categories. Note that a total column for all Grade Centre columns is created by default.
A Weighted Column calculates and displays a grade based on the result of selected columns and categories, and their respective percentages. You need to select which columns to include or select via categories. You need to add in the percentage for each column/category and ensure the total is 100%. If using categories there is an option to drop or use only the highest/lowest grades.