How to include extensions when adding phone contacts?

[martini-in-hand]

New to the forum, not sure this is the place for my question.
How do yo indicate an extension number in your phone contacts. When I carried over the old contacts from my Blackberry, the numbers all ran together and I received an error message when i tried to phone.

Also, is it the same process when you add from the phone as it is on adding from Google contacts?

Thanks,
martini-in-hand