When adding a pub.dev dependency for a custom widget it does not import

I am trying to create a custom widget that uses the pub.dev package table_celndar
(https://pub.dev/packages/table_calendar/install)

In the area where we need to add the dependencies I pasted the information and copied from the website. (circled at the bottom-right in the attached screenshot)

Then I wrote my import statement in my code area. (circled in the middle of the attached screenshot).

But for some reason, the import statement is underlined in red and the package is not imported...