One cool feature of Google Sheets is the ability to insert and add new columns to your data tables. This is especially useful if you have a general format that you want to maintain throughout the table.
Step #1: Select Your "Parent" Column
First, you will click anywhere on a column that will be to the right or left of your new one. I personally like call it the "Parent" column, but that isn't some sort of official nomenclature.
Step #2: Click "Insert"
Next, click "Insert", located in the header section. Then, the drop-down menu will show two options for inserting new columns; Column Left and Column Right.
Column Left: Adds a new column to the left of the "Parent".
Column Right: Adds a new column to the right of the "Parent".
Note: As you can see, you also have the option to insert rows.