cr:5.2.3c

If an effect allows a source to attack additional times or a set number of times, it refers to activating an ability on the source with the attack ability.[8.3.1]

Example: Twinning Blade has the text “You may attack an additional time with target sword this turn,” which allows the player to activate an activated ability (with the attack ability) on the target sword an additional time past its LIMIT.

Example: Flurry has the text “. . . you may attack with the weapon twice this turn,” which allows the player to activate an activated ability (with the attack ability) on the target sword up to two times.