Newly added Group column does not have drop down

I added a group column to my foundation sheet in google sheets, but i dont know what this below means in the article on adding a group column - there is no drop down in my new group column

Note: you can add the column for Group wherever you want it to appear, but we don’t recommend to the right or left of the Category column because it will add the data validation (dropdown menu) formatting and it’s meant to be a read-only column.

There should be no drop down in your new group column. The note is just warning you that if you insert a new column to the left or right of the existing Category column it will include the Category drop down validation in your new Group column, which you don’t want to do. If you successfully added your new Group column and there is no drop down, you have done it correctly.